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SYSTEMS AND METHODS FOR PROVIDING SYNCI-IRONIZATION SERVICES FOR
UNITS OF INFORMATION MANAGEABLE BY A HARDWARE/SOFTWARE
INTERFACE SYSTEM
FIELD OF THE INVENTION
100031 The present invention relates generally to the field of information
storage and
retrieval, and, more particularly, to an active storage platform for
organizing, searching. and
sharing different types of data in a computerized system.
= BACKGROUND
[00041 Individual disk capacity has been growing at roughly seventy percent
(70%) per
year over the last decade. Moore's law accurately predicted the tremendous
gains in central
processing unit (CPU) power that has occurred over the years- Wired and
wireless technologies
have provided tremendous connectivity and bandwidth. Presuming current trends
continue,
within several years the average laptop computer will possess roughly one
terabyte (TB) of
storage and contain millions of files, and 500 gigabyte (GB) drives will
become commonplace.
[00051 Consumers use their computers primarily for communication and
organizing
personal information, whether it is traditional personal information manager
(PIM) style data or
media such as digital music or photographs. The amount of digital content, and
the ability to
store the raw bytes, has increased tremendously; however the methods available
to consumers for
organizing and unifying this data has not kept pace. Knowledge workers spend
enormous
amounts of time managing and sharing information, and some studies estimate
that knowledge
workers spend 15-25% of their time on non-productive information related
activities. Other
studies estimate that a typical knowledge worker spends about 2.5 hours per
day searching for
information.
[00061 Developers and information technology (IT) departments invest
significant
amounts of time and money in building their own data stores for common storage
abstractions to
represent such things as people, places, times, and events. Not only does this
result in duplicated
work, but it also creates islands of common data with no mechanisms for common
searching or
sharing of that data. Just consider how many address books can exist today on
a computer
TM, -
running the Microsoft Windows operating system. Many applications, such as e-
mail clients and
personal finance programs, keep individual address books, and there is little
sharing among
applications of the address book data that each such program individually
maintains.
TM
Consequently, a finance program (like Microsoft Money) does not share
addresses for payees
TM
with the addresses maintained in an email contact folder (like the one in
Microsoft Outlook).
Indeed, many users have multiple devices and logically should synchronize
their personal data
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amongst themselves and across a wide variety of additional sources, including
cell phones to
commercial services such as MSN and AOL; nevertheless, collaboration of shared
documents is
largely achieved by attaching documents to e-mail messages-that is, manually
and inefficiently.
100071 One reason for this lack of collaboration is that traditional
approaches to the
organization of information in computer systems have centered on the use of
file-folder-and-
directory-based systems ("file systems") to organize pluralities of files into
directory hierarchies
of folders based on an abstraction of the physical organization of the storage
medium used to
store the files. The Multics operating system, developed during the 1960s, can
be credited with
pioneering the use of the files, folders, and directories to manage storable
units of data at the
operating system level. Specifically, Multics used symbolic addresses within a
hierarchy of files
(thereby introducing the idea of a file path) where physical addresses of the
files were not
transparent to the user (applications and end-users). This file system was
entirely unconcerned
with the file format of any individual file, and the relationships amongst and
between files was
deemed irrelevant at the operating system level (that is, other than the
location of the file within
the hierarchy). Since the advent of Multics, storable data has been organized
into files, folders,
and directories at the operating system level. These files generally include
the file hierarchy
itself (the "directory") embodied in a special file maintained by the file
system. This directory,
in turn, maintains a list of entries corresponding to all of the other files
in the directory and the
nodal location of such files in the hierarchy (herein referred to as the
folders). Such has been the
state of the art for approximately forty years.
[00081 However, while providing a reasonable representation of information
residing in
the computer's physical storage system, a file system is nevertheless an
abstraction of that
physical storage system, and therefore utilization of the files requires a
level of indirection
(interpretation) between what the user manipulates (units having context,
features, and
relationships to other units) and what the operating system provides (files,
folders, and
directories). Consequently, users (applications and/or end-users) have no
choice but to force
units of information into a file system structure even when doing so is
inefficient, inconsistent, or
otherwise undesirable. Moreover, existing file systems know little about the
structure of data
stored in individual files and, because of this, most of the information
remains locked up in files
that may only be accessed (and comprehensible) to the applications that wrote
them.
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Consequently, this lack of schematic description of information, and
mechanisms for managing
information, leads to the creation of silos of data with little data sharing
among the individual
silos. For example, many personal computer (PC) users have more than five
distinct stores that
contain information about the people they interact with on some level-for
example, Outlook
Contacts, online account addressees, Windows Address Book, Quicken Payees, and
instant
messaging (IM) buddy lists-because organizing files presents a significant
challenge to these
PC users. Because most existing file systems utilize a nested folder metaphor
for organizing files
and folders, as the number of files increases the effort necessary to maintain
an organization
scheme that is flexible and efficient becomes quite daunting. In such
situations, it-would be very
useful to have multiple classifications of a single file; however, using hard
or soft links in
existing file systems is cumbersome and difficult to maintain.
[00091 Several unsuccessful attempts to address the shortcomings of file
systems have
been made in the past. Some of these previous attempts have involved the use
of content
addressable memory to provide a mechanism whereby data could be accessed by
content rather
than by physical address. However, these efforts have proven unsuccessful
because, while
content addressable memory has proven useful for small-scale use by devices
such as caches and
memory management units, large-scale use for devices such as physical storage
media has not
yet been possible for a variety of reasons, and thus such a solution simply
does not exist. Other
attempts using object-oriented database (OODB) systems have been made, but
these attempts,
while featuring strong database characteristics and good non-file
representations, were not
effective in handling file representations and could not replicate the speed,
efficiency, and
simplicity of the file and folder based hierarchical structure at the
hardware/software interface
system level. Other efforts, such as those that attempted to use SmallTalk
(and other
derivatives), proved to be quite effective at handling file and non-file
representations but lacked
database features necessary to efficiently organize and utilize the
relationships that exist between
the various data files, and thus the overall efficiency of such systems was
unacceptable. Yet
other attempts to use BeOS (and other such operating systems research) proved
to be inadequate
at handling non-file representations-the same core shortcoming of traditional
file systems-
despite being able to adequately represent files while providing some
necessary database
features.
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[00101 Database technology is another area of the art in which similar
challenges exits.
For example, while the relational database model has been a great commercial
success, in truth
independent soft ware vendors (ISV) generally exercise a small portion of the
functionality
TM
available in relational database software products (such as Microsoft SQL
Server). Instead, most
of an application's interaction with such a product is in the form of simple
"gets" and "puts".
While there are a number of readily apparent reasons for this such as being
platform or
database agnostic-one key reason that often goes unnoticed is that the
database does not
necessarily provide the exact abstractions that a major business application
vendor really needs.
For example, while the real world has the notion of "items", such as
"customers" or "orders"
(along with an order's embedded "line items" as items in and of themselves),
relational databases
only talk in terms of tables and rows. Consequently, while the application may
desire to have
aspects of consistency, locking, security, and/or triggers at the item level
(to name a few),
generally databases provide these features only at the table/row level. While
this may work fine
if each item gets mapped to a single row in some table in the database, in the
case of an order
with multiple line items there may be reasons why an item actually gets mapped
to multiple
tables and, when that is the case, the simple relational database system does
not quite provide the
right abstractions. Consequently, an application must build logic on top of
the database to
provide these basic abstractions. In other words, the basic relational model
does not provide a
sufficient platform for storage of data on which higher-level applications can
easily be developed
because the basic relational model requires a level of indirection between the
application and the
storage system-where the semantic structure of the data might only be visible
in the application
in certain instances. While some database vendors are building higher-level
functionality into
their products--such as providing object relational capabilities, new
organizational models, and
the like--none have yet to provide the kind of comprehensive solution needed,
where a truly
comprehensive solution is one which provides both useful data model
abstractions (such as
"Items," "Extensions," "Relationships," and so on) for useful domain
abstractions (such as
"Persons," "Locations," "Events," etc.).
(00111 In view of the foregoing deficiencies in existing data storage and
database
technologies, there is a need for a new storage platform that provides an
improved ability to
organize, search, and share all types of data in a computer system-a storage
platform that
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extends and broadens the data platform beyond existing file systems and
database systems, and
that is designed to be the store for all types of data. The present invention,
together with the
related inventions incorporated by reference earlier herein, satisfies this
need.
SUMMARY
[0012] The following summary provides an overview of various aspects of the
invention described in the context of the related inventions incorporated-by-
reference earlier
herein (the "related inventions"). This summary is not intended to provide an
exhaustive
description of all of the important aspects of the invention, nor to define
the scope of the
invention. Rather, this summary is intended to serve as an introduction to the
detailed
description and figures that follow.
[00131 The present invention, as well as the related inventions, are
collectively directed
to a storage platform for organizing, searching, and sharing data The storage
platform of the
present invention extends and broadens the concept of data storage beyond
existing file systems
and database systems, and is designed to be the store for all types of data
including structured,
non-structured, or semi-structured data.
[0014] The storage platform of the present invention comprises a data store
implemented on a database engine. The database engine comprises a relational
database engine
with object relational extensions. The data store implements a data model that
supports
organization, searching, sharing, synchronization, and security of data.
Specific types of data are
described in schemas, and the platform provides a mechanism to extend the set
of schemas to
define new types of data (essentially subtypes of the basic types provides by
the schemas). A
synchronization capability facilitates the sharing of data among users or
systems. File-system-
like capabilities are provided that allow interoperability of the data store
with existing file
systems but without the limitation of such traditional file systems. A change
tracking
mechanism provides the ability track changes to the data store. The storage
platform further
comprises a set of application program interfaces that enable applications to
access all of the
foregoing capabilities of the storage platform and to access the data
described in the schemas.
[0015] The data model implemented by the data store defines units of data
storage in
terms of items, elements, and relationships. An item is a unit of data
storable in a data store and
can comprise one or more elements and relationships. An element is an instance
of a type
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comprising one or more fields (also referred to herein as a property). A
relationship is a link
between two items. (As used herein, these and other specific terms may be
capitalized in order
to offset them from other terms used in close proximity; however, there is no
intention
whatsoever to distinguish between a capitalized term, e.g. "Item", and the
same term when not
capitalized, e.g., "item", and no such distinction should be presumed or
implied.)
[0016[ The computer system further comprises a plurality of Items where each
Item
constitutes a discrete storable unit of information that can be manipulated by
a
hardware/software interface system; a plurality of Item Folders that
constitute an organizational
structure for said Items; and a hardware/software interface system for
manipulating a plurality of
Items and wherein each Item belongs to at least one Item Folder and may belong
to more than
one Item Folder.
[0017] An Item or some of the Item's property values maybe computed
dynamically as
opposed to being derived from a persistent store. In other words, the
hardware/software interface
system does not require that the Item be stored, and certain operations are
supported such as the
ability to enumerate the current set of Items or the ability to retrieve an
Item given its identifier
(which is more fully described in the sections that describe the application
programming
interface, or API) of the storage platform - for example, an Item might be the
current location of
a cell phone or the temperature reading on a temperature sensor. The
hardware/software
interface system may manipulate a plurality of Items, and may further comprise
Items
interconnected by a plurality of Relationships managed by the
hardware/software interface
system.
[0018] A hardware/software interface system for the computer system further
comprises a core schema to define a set of core Items which said
hardware/software interface
system understands and can directly process in a predetermined and predictable
way. To
manipulate a plurality of Items, the computer system interconnects said Items
with a plurality of
Relationships and manages said Relationships at the hardware/software
interface system level.
[0019] The API of the storage platform provides data classes for each item,
item
extension, and relationship defined in the set of storage platform schemas. In
addition, the
application programming interface provides a set of framework classes that
define a common set
of behaviors for the data classes and that, together with the data classes,
provide the basic
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programming model for the storage platform API. The storage platform API
provides
a simplified query model that enables application programmers to form queries
based
on various properties of the items in the data store, in a manner that
insulates the
application programmer from the details of the query language of the
underlying
database engine. The storage platform API also collects changes to an item
made
by an application program and then organizes them into the correct updates
required
by the database engine (or any kind of storage engine) on which the data store
is
implemented. This enables application programmers to make changes to an item
in
memory, while leaving the complexity of data store updates to the API.
[0020] Through its common storage foundation and schematized data, the
storage platform of the present invention enables more efficient application
development for consumers, knowledge workers and enterprises. It offers a rich
and
extensible application programming interface that not only makes available the
capabilities inherent in its data model, but also embraces and extends
existing file
system and database access methods.
[0021] As part of this overarching structure of interrelated inventions
(described in detail in Section II of the Detailed Description), the present
invention is
specifically directed to the Synchronization APIs (described in detail in
Section III of
the Detailed Description). Other features and advantages of the invention may
become apparent from the following detailed description of the invention and
accompanying drawings.
According to one aspect of the present invention, there is provided a
storage platform system including a processor and a computer readable storage
medium, said storage system comprising: instructions for an operating system,
the
operating system including a kernel, wherein the kernel includes a database
management program that encapsulates a file system, the database management
program that encapsulates with the file system configured to store data in the
file
system as file streams, generate items that include metadata for the file
streams and
store the items in the database management program, the database management
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program including a base schema and a mechanism configured to extend the base
schema to define a schema for the data, and divide the data into programmably
defined change units based on the schema for the data, wherein a change unit
is a
smallest piece of schema that is individually tracked by the database
management
program integrated with the file system and the size of a change unit is
adjustable;
wherein the database management system is configured to generate and store
state
information for files stored in a non-synch-aware remote computer system,
wherein
the state information includes change information for the files stored in the
non-
synch-aware remote computer system, wherein the non-synch-aware remote
computer system does not include a synchronization subsystem that is
synchronization compatible with a synchronization subsystem executing on the
processor; the operating system further including the synchronization
subsystem
configured to compare status information for items stored in the database
management program to state information for corresponding files stored in the
non-
synch-aware remote computer system, the synchronization subsystem further
configured to determine which files stored in the non-synch-aware remote
computer
system need updating based on the comparison, the synchronization subsystem
further configured to translate items into files formatted for storage in the
non-synch-
aware remote computer system, the synchronization subsystem further configured
to
send the files formatted for storage in the non-synch to the remote computer
system,
and the synchronization subsystem further configured to update the state
information
for files stored in the non-synch-aware remote computer system, wherein the
non-
synch-aware remote computer system is configured to receive the files and
store
them in a file system.
According to another aspect of the present invention, there is provided
a method for synchronizing data stored in a computer system, said method
comprising: executing an operating system that includes a kernel, the kernel
including a database management program that encapsulates a file system,
wherein
the database management program includes a base schema and a mechanism to
extend the base schema to define a schema for data; storing, by the database
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management program that encapsulates the file system, data in the file system
as file
streams; generating, by the database management program that encapsulates the
file system, items that include metadata for the file streams, wherein the
metadata is
defined by the schema for the data; storing the items in the database
management
program; dividing, by the database management program that encapsulates the
file
system, said data into programmably defined change units based on the schema
for
the data, wherein a change unit is a smallest piece of schema that is
individually
tracked by the database management program that encapsulates the file system
and
the size of a change unit is adjustable; generating, by the database
management
program, state information for files stored in a non-synch-aware remote
computer
system, wherein the state information includes change information for the
files stored
in a non-synch-aware remote computer system, wherein the non-synch-aware
remote computer system does not include a synchronization subsystem that is
synchronization compatible with the database management program; comparing, by
the database management program, change unit information for items stored in
the
database management program to state information for corresponding files
stored in
a non-synch-aware remote computer system; determining, by the database
management program, which files stored in the non-synch-aware remote computer
system need updating based on the comparison; translating, by the database
management program, items into files formatted for storage in the non-synch-
aware
remote computer system; sending, by the database management program, the files
formatted for storage in the non-synch-aware remote computer system to the
remote
computer system; and updating, by the database management program, the state
information for files stored in the non-synch-aware remote computer system,
wherein
the non-synch-aware remote computer system is configured to receive the files
and
store them in a file system.
According to still another aspect of the present invention, there is
provided a method for synchronizing data, said method comprising: executing an
operating system that includes a kernel, the kernel including a database
management
program that encapsulates a file system; storing, by the database management
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program that encapsulates the file system, data in the file system as file
streams;
generating, by the database management program that encapsulates the file
system,
items associated with the file streams that include metadata for the file
streams,
wherein the metadata is defined by the schema for the data, further wherein
the items
conform to a schema derived from a base schema, the schema defining a size of
a
change unit, further wherein a change unit is the smallest piece of schema
that is
individually tracked by the database management program that encapsulates the
file
system; storing the items in the database management program; generating, by
the
database management program, state information for files stored in a non-synch-
aware remote computer system, wherein the state information includes change
information for the files stored in a non-synch-aware remote computer system,
wherein the non-synch-aware remote computer system does not include a
synchronization subsystem that is synchronization compatible with the database
management program; comparing, by the database management program, change
unit information for items stored in the database management program to state
information for corresponding files stored in a non-synch-aware remote
computer
system; determining, by the database management program, which items in the
database management program need updating based on the comparison; receiving
files corresponding to the items that need updating from the non-synch- aware
remote computer system; translating, by the database management program, files
corresponding to the items that need updating into items; storing, by the
database
management program, the items obtained from the files corresponding to the
items
that need updating in the database management program; storing, by the
database
management program, updated state information for files stored in a non-synch-
aware remote computer system.
According to yet another aspect of the present invention, there is
provided a computer-readable storage medium having stored thereon computer-
readable instructions for execution by a computer, the instructions
comprising:
instructions for an operating system, the operating system including a kernel
and a
shell, wherein applications execute on the shell of the operating system; the
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instructions for the operating system including a database management program
that
encapsulates a file system, wherein the database management program that
encapsulates the file system is part of the kernel of the operating system;
the
instructions for the database management program that encapsulates the file
system
configured to store data as file streams in the file system and generate items
for the
file streams that include metadata for the file streams, wherein the format of
the
metadata conforms to one of a plurality of schemas, each schema of the
plurality is
derived from a base schema, further wherein each schema of the plurality
includes
programmably defined change units, wherein a change unit is a smallest piece
of
schema that is individually tracked by the database management program that
encapsulates the file system; instructions for generating state information
for files
stored in a non-synch-aware remote computer system, wherein the state
information
includes change information for the files stored in a non-synch-aware remote
computer system, wherein the non-synch-aware remote computer system does not
include a synchronization subsystem that is synchronization compatible with
the
database management program; instructions for comparing change unit
information
for items stored in the database management program to state information for
corresponding files stored in a non-synch-aware remote computer system;
instructions for determining which files stored in the non-synch-aware remote
computer system need updating based on the comparison; instructions for
translating
items into files formatted for storage in the non-synch- aware remote computer
system; instructions for sending the files formatted for storage in the non-
synch-
aware computer system to the remote computer system; and instructions for
updating
the state information for files stored in the non-synch-aware remote computer
system,
wherein the non-synch-aware remote computer system is configured to receive
the
files and store them in a file system.
According to a further aspect of the present invention, there is provided
a computer-readable storage medium having stored thereon computer-readable
instructions for synchronizing data for execution by a computer, the
instructions
comprising: instructions for executing an operating system that include
instructions
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for a kernel, the instructions for the kernel including instructions for a
file system
encapsulated by a database management program, wherein the instructions for
the
database management program include instructions for a base schema and a
mechanism to extend the base schema to define a schema for data; the
instructions
for the kernel of the operating system including instructions for storing data
in the file
system as file streams; the instructions for the kernel of the operating
system
including instructions for generating items that include metadata for the file
streams,
wherein the metadata is defined by the schema for the data; the instructions
for the
kernel of the operating system including instructions for instructions for
storing the
items in the database management program; the instructions for the kernel of
the
operating system including instructions for dividing said data into
programmably
defined change units based on the schema for the data, wherein a change unit
is a
smallest piece of schema that is individually tracked by the database
management
program that encapsulates the file system and the size of a change unit is
adjustable;
the instructions for the database management program including instructions
for
sequentially enumerating changes to said data and tracking said changes on a
per
change unit basis; the instructions for the database management program
including
instructions for generating state information for files stored in a non-synch-
aware
remote computer system, wherein the state information includes change
information
for the files stored in a non-synch-aware remote computer system, wherein the
non-
synch-aware remote computer system does not include a synchronization
subsystem
that is synchronization compatible with the database management program; the
instructions for the database management program including instructions for
comparing change unit information for items stored in the database management
program to state information for corresponding files stored in a non-synch-
aware
remote computer system; the instructions for the database management program
including instructions for determining which files stored in the non-synch-
aware
remote computer system need updating based on the comparison; the instructions
for
the database management program including instructions for translating items
into
files formatted for storage in the non-synch-aware remote computer system; the
instructions for the database management program including instructions for
sending
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the files formatted for storage in the non-synch-aware remote computer system
to the
remote computer system; and the instructions for the database management
program
including instructions for updating the state information for files stored in
the non-
synch-aware remote computer system, wherein the non-synch-aware remote
computer system is configured to receive the files and store them in a file
system.
According to yet a further aspect of the present invention, there is
provided computer-readable storage medium having stored thereon computer
readable instructions for synchronizing data stored for execution by a
computer, said
computer-readable storage medium comprising: instructions for executing an
operating system that includes a kernel, the kernel including a file system
encapsulated by a database management program; the instructions for the kernel
of
the operating system including instructions for storing data in the file
system as file
streams; the instructions for the kernel of the operating system including
instructions
for generating items associated with the file streams that include metadata
for the file
streams, wherein the metadata is defined by the schema for the data, further
wherein
the items conform to a schema derived from a base schema, the schema defining
a
size of a change unit, further wherein a change unit is the smallest piece of
schema
that is individually tracked by the database management program integrated
with the
file system; instructions for storing the items in the database management
program;
instructions for generating state information for files stored in a non-synch-
aware
remote computer system, wherein the state information includes change
information
for the files stored in a non-synch-aware remote computer system, wherein the
non-
synch-aware remote computer system does not include a synchronization
subsystem
that is compatible with the database management program; instructions for
comparing change unit information for items stored in the database management
program to state information for corresponding files stored in a non-synch-
aware
remote computer system; instructions for determining which items in the
database
management program need updating based on the comparison; instructions for
receiving files corresponding to the items that need updating from the non-
synch-
aware remote computer system; instructions for translating files corresponding
to the
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items that need updating into items; instructions for storing the items
obtained from
the files corresponding to the items that need updating in the database
management
program; instructions for storing updated state information for files stored
in a non-
synch-aware remote computer system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The foregoing summary, as well as the following detailed description of
the invention, is better understood when read in conjunction with the appended
drawings. For the purpose of illustrating the invention, there is shown in the
drawings
exemplary embodiments of various aspects of the invention; however, the
invention is
not limited to the specific methods and instrumentalities disclosed. In the
drawings:
[0023] Fig. 1 is a block diagram representing a computer system in which
aspects of the present invention may be incorporated;
[0024] Fig. 2 is a block diagram illustrating a computer system divided into
three component groups: the hardware component, the hardware/software
interface
system component, and the application programs component;
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[0025] Fig. 2A illustrates the traditional tree-based hierarchical structure
for files
grouped in folders in a directory in a file-based operating system;
[0026] Fig. 3 is a block diagram illustrating a storage platform;
[0027] Fig. 4 illustrates the structural relationship between Items, Item
Folders, and
Categories;
[0028] Fig. 5A is a block diagram illustrating the structure of an Item;
[0029] Fig. 5B is a block diagram illustrating the complex property types of
the Item of
Fig. 5A;
[0030] Fig. 5C is a block diagram illustrating the "Location" Item wherein its
complex
types are further described (explicitly listed);
[0031] Fig. 6A illustrates an Item as a subtype of the Item found in the Base
Schema;
[0032] Fig. 6B is a block diagram illustrating the subtype Item of Fig. 6A
wherein its
inherited types are explicitly listed (in addition to its immediate
properties);
[0033] Fig. 7 is a block diagram illustrating the Base Schema including its
two top-
level class types, Item and PropertyBase, and the additional Base Schema types
derived
therefrom;
[0034] Fig. 8A is a block diagram illustrating Items in the Core Schema;
[0035] Fig. 8B is a block diagram illustrating the property types in the Core
Schema;
[0036] Fig. 9 is a block diagram illustrating an Item Folder, its member
Items, and the
interconnecting Relationships between the Item Folder and its member Items;
[0037] Fig. 10 is a block diagram illustrating a Category (which, again, is an
Item
itself), its member Items, and the interconnecting Relationships between the
Category and its
member Items;
[0038] Fig. 11 is a diagram illustrating a reference type hierarchy of the
data model of
the storage platform;
[0039] Fig. 12 is a diagram illustrating how relationships are classified;
[0040] Fig. 13 is a diagram illustrating a notification mechanism;
[0041] Fig. 14 is a diagram illustrating an example in which two transactions
are both
inserting a new record into the same B-Tree;
[0042] Fig. 15 illustrates a data change detection process;
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[0043] Fig. 16 illustrates an exemplary directory tree;
[0044] Fig. 17 shows an example in which an existing folder of a directory-
based file
system is moved into the storage platform data store;
[0045] Fig. 18 illustrates the concept of Containment Folders;
[0046] Fig. 19 illustrates the basic architecture of the storage platform API;
[0047] Fig. 20 schematically represents the various components of the storage
platform
API stack;
[0048] Fig. 21A is a pictorial representation of an exemplary Contacts Item
schema;
[0049] Fig. 21B is a pictorial representation of the Elements for the
exemplary Contacts
Item schema of Fig. 21A;
[0050] Fig. 22 illustrates the runtime framework of the storage platform API;
[0051] Fig. 23 illustrates the execution of a "FindAll" operation;
[0052] Fig. 24 illustrates the process by which storage platform API classes
are
generated from the storage platform Schema;
[0053] Fig. 25 illustrates a schema on which a File API is based;
[0054] Fig. 26 is a diagram illustrating an access mask format used for data
security
purposes;
[0055] Fig. 27 (parts a, b, and c) depicts a new identically protected
security region
being carved out of an existing security region;
[0056] Fig. 28 is a diagram illustrating the concept of an Item search view;
[0057] Fig. 29 is a diagram illustrating an exemplary Item hierarchy;
[0058] Fig. 30A illustrates an interface Interface1 as a conduit through which
first and
second code segments communicate;
[0059] Fig. 30B illustrates an interface as comprising interface objects 11
and 12 which
enable first and second code segments of a system to communicate via medium M;
[0060] Fig. 31A illustrates how the function provided by interface Interface1
maybe
subdivided to convert the communications of the interface into multiple
interfaces InterfacelA,
Interface 113, Interface 1C;
[0061] Fig. 31B illustrates how the function provided by interface I1 maybe
subdivided into multiple interfaces Ila, Ilb, Ile;
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[0062] Fig. 32A illustrates a scenario where a meaningless parameter precision
can be
ignored or replaced with an arbitrary parameter;
[00631 Fig. 32B illustrates a scenario where an interface is replaced by a
substitute
interface that is defined to ignore or add parameters to an interface;
[0064] Fig. 33A illustrates a scenario where a 1st and 2nd Code Segments are
merged
into a module containing them both;
[0065] Fig. 33B illustrates a scenario where part or all of an interface may
be written
inline into another interface to form a merged interface.
[0066] Fig. 34A illustrates how one or more pieces of middleware might convert
communications on the first interface to conform them to one or more different
interfaces;
[0067] Fig. 34B illustrates how a code segment can be introduced with an
interface to
receive the communications from one interface but transmit the functionality
to second and third
interfaces;
[0068] Fig. 35A illustrates how a just-in-time compiler (JIT) might convert
communications from one code segment to another code segment;
[0069] Fig. 35B illustrates a JIT method of dynamically rewriting one or more
interfaces may be applied to dynamically factor or otherwise alter said
interface;
[0070] Fig. 36 illustrates a three instances of a common data store and the
components
for synchronizing them; and
[0071] Fig. 37 illustrates one embodiment of the present invention that
presumes a
simple adapter that is unaware of how state is calculated or its associated
metadata is exchanged.
[Remainder of Page Intentionally Left Blank]
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DETAILED DESCRIPTION
TABLE OF CONTENTS
I. INTRODUCTION
...............................................................................
......................... - 18-
A. EXEMPLARY COMPUTING ENVIRONMENT
............................................ 18-
B. TRADITIONAL FILE-BASED STORAGE
..................................................... 22-
II. WINFS STORAGE PLATFORM FOR ORGANIZING, SEARCHING, AND
SHARING DATA
...............................................................................
..........................- 24-
A. GLOSSARY
...............................................................................
......................- 24-
B. STORAGE PLATFORM OVERVIEW
............................................................ 25-
C. THE DATA MODEL
...............................................................................
........- 26-
1 . Items
...............................................................................
.......................- 28-
2. Item Identification
...............................................................................
..- 32-
3. Item Folders and Categories
.................................................................- 32-
4. Schemas
...............................................................................
.................- 34-
a) Base Schema
.............................................................................-
34-
b) Core Schema
.............................................................................-
35-
5. Relationships
...............................................................................
..........- 37-
a) Relationship Declaration
........................................................... - 38-
b) Holding Relationship
................................................................ - 39-
C) Embedding Relationships
......................................................... - 40-
d) Reference Relationships
............................................................ - 41-
e) Rules and Constraints
............................................................... - 42-
f) Ordering of Relationships
.......................................................... - 42 -
6. Extensibility
...............................................................................
........... - 48-
a) Item extensions
......................................................................... - 49-
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b) Extending NestedElement types
............................................... - 53-
D. DATABASE ENGINE
...............................................................................
......- 55-
1 . Data Store Implementation Using UDTs
............................................... 56-
2. Item Mapping
...............................................................................
.........- 57-
3. Extension Mapping
...............................................................................
- 58-
4. Nested Element Mapping
...................................................................... - 58-
5. Object Identity
...............................................................................
.......- 58-
6. SQL Object Naming
.............................................................................-
58-
7. Column Naming
...............................................................................
.....- 59-
8. Search Views
...............................................................................
.........- 60-
a) Item
...............................................................................
............ - 61-
(1) Master Item Search View ..............................................- 61-
(2) Typed Item Search Views .............................................- 61-
b) Item Extensions
......................................................................... - 62-
(1) Master Extension Search View .....................................-62-
(2) Typed Extension Search Views .................................... - 63-
C) Nested Elements
........................................................................ - 63-
d) Relationships
............................................................................. -
64-
(1) Master Relationship Search View ................................. - 64-
(2) Relationship Instance Search Views ............................. - 64-
e) - 65 -
10. Change Tracking & Tombstones
..........................................................- 66-
a) Change Tracking
.......................................................................- 66-
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(1) Change Tracking in "Master" Search Views ................- 66-
(2) Change Tracking in "Typed" Search Views ................. - 67-
b) Tombstones
...............................................................................
-68-
(1) Item Tombstones
...........................................................- 68-
(2) Extension Tombstones .................................................. -
69-
(3) Relationships Tombstone .............................................. -
69-
(4) Tombstone Cleanup ...................................................... -
70-
11. Helper APIs and Functions
................................................................... - 70-
a) Function [System.Storage].GetItem
.......................................... - 70-
b) Function [System. Storage]. GetExtension .................................-
70-
c) Function [System. Storage]. GetRelationship ............................. -
71-
12. Metadata
...............................................................................
................. - 71-
a) Schema Metadata
......................................................................- 71-
b) Instance Metadata
..................................................................... - 71-
E. SECURITY
...............................................................................
........................ - 71-
F. NOTIFICATIONS AND CHANGE TRACKING
............................................ 72-
G. TRADITIONAL FILE SYSTEM INTEROPERABILITY ............................... 73-
H. STORAGE PLATFORM API 74-
111. SYNCHRONIZATION API
...............................................................................
..........- 80-
A. SYNCHRONIZATION OVERVIEW
.............................................................. - 81-
1 . Storage-Platform-to-Storage-Platform Synchronization
......................- 81-
a) Synchronization (Sync) Controlling Applications .................... - 82-
b) Schema annotation
....................................................................- 83 -
c) Sync Configuration
................................................................... - 84-
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(1) Community Folder - Mappings ...................................... 85-
(2) Profiles
.......................................................................... -
86-
(3) Schedules ..................................................... 87-
d) Conflict Handling
...................................................................... - 87-
(1) Conflict Detection
.........................................................- 87-
(a) Knowledge- Based Conflicts -87-
(b) Constraint-Based Conflicts -88-
(2) Conflict Processing
....................................................... - 88-
(a) Automatic Conflict Resolution _89-
(b) Conflict Logging -89-
(c) Conflict Inspection and Resolution _90-
(d) Convergence of Replicas and Propagation of
Conflict Resolutions _90-
2. Synchronizing to Non-Storage Platform Data Stores
...........................- 91-
a) Sync Services
............................................................................ -
91-
(1) Change Enumeration ..................................................... -
91-
(2) Change Application ...................................................... -
92-
(3) Conflict Resolution
....................................................... - 93-
b) Adapter Implementation
........................................................... - 93-
3. Security
...............................................................................
.................. - 94-
4. Manageability
...............................................................................
........- 94-
B. SYNCHRONIZATION API OVERVIEW
....................................................... 95 -
1. General Terminology
............................................................................ -
95-
2. Synchronization API
Principals............................................................- 97-
C. SYNCHRONIZATION API SERVICES
.......................................................... 99-
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1. Change Enumeration
.............................................................................-
99-
2. Change Application
............................................................................-
100-
3. Sample Code
...............................................................................
........- 100-
4. Methods of API Synchronization
........................................................- 104-
D. ADDITIONAL ASPECTS OF THE SYNC SCHEMA .................................-
106-
IV. CONCLUSION
...............................................................................
............................- 108-
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I. INTRODUCTION
[0072] The subject matter of the present invention is described with
specificity to meet
statutory requirements. However, the description itself is not intended to
limit the scope of this
patent. Rather, the inventors have contemplated that the claimed subject
matter might also be
embodied in other ways, to include different steps or combinations of steps
similar to the ones
described in this document, in conjunction with other present or future
technologies. Moreover,
although the term "step" may be used herein to connote different elements of
methods employed,
the term should not be interpreted as implying any particular order among or
between various
steps herein disclosed unless and except when the order of individual steps is
explicitly
described.
A. EXEMPLARY COMPUTING ENVIRONMENT
[0073] Numerous embodiments of the present invention may execute on a
computer.
Fig. 1 and the following discussion is intended to provide a brief general
description of a suitable
computing environment in which the invention may be implemented. Although not
required,
various aspects of the invention may be described in the general context of
computer executable
instructions, such as program modules, being executed by a computer, such as a
client
workstation or a server. Generally, program modules include routines,
programs, objects,
components, data structures and the like that perform particular tasks or
implement particular
abstract data types. Moreover, the invention may be practiced with other
computer system
configurations, including hand held devices, multi processor systems,
microprocessor based or
programmable consumer electronics, network PCs, minicomputers, mainframe
computers and
the like. The invention may also be practiced in distributed computing
environments where tasks
are performed by remote processing devices that are linked through a
communications network.
In a distributed computing environment, program modules may be located in both
local and
remote memory storage devices.
[0074] As shown in Fig. 1, an exemplary general purpose computing system
includes a
conventional personal computer 20 or the like, including a processing unit 21,
a system memory
22, and a system bus 23 that couples various system components including the
system memory
to the processing unit 21. The system bus 23 may be any of several types of
bus structures
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including a memory bus or memory controller, a peripheral bus, and a local bus
using any of a
variety of bus architectures. The system memory includes read only memory
(ROM) 24 and
random access memory (RAM) 25. A basic input/output system 26 (BIOS),
containing the basic
routines that help to transfer information between elements within the
personal computer 20,
such as during start up, is stored in ROM 24. The personal computer 20 may
further include a
hard disk drive 27 for reading from and writing to a hard disk, not shown, a
magnetic disk drive
28 for reading from or writing to a removable magnetic disk 29, and an optical
disk drive 30 for
reading from or writing to a removable optical disk 31 such as a CD ROM or
other optical
media. The hard disk drive 27, magnetic disk drive 28, and optical disk drive
30 are connected to
the system bus 23 by a hard disk drive interface 32, a magnetic disk drive
interface 33, and an
optical drive interface 34, respectively. The drives and their associated
computer readable media
provide non volatile storage of computer readable instructions, data
structures, program modules
and other data for the personal computer 20. Although the exemplary
environment described
herein employs a hard disk, a removable magnetic disk 29 and a removable
optical disk 31, it
should be appreciated by those skilled in the art that other types of computer
readable media
which can store data that is accessible by a computer, such as magnetic
cassettes, flash memory
cards, digital video disks, Bernoulli cartridges, random access memories
(RAMs), read only
memories (ROMs) and the like may also be used in the exemplary operating
environment.
Likewise, the exemplary environment may also include many types of monitoring
devices such
as heat sensors and security or fire alarm systems, and other sources of
information.
[0075] A number of program modules may be stored on the hard disk, magnetic
disk
29, optical disk 31, ROM 24 or RAM 25, including an operating system 35, one
or more
application programs 36, other program modules 37 and program data 38. A user
may enter
commands and information into the personal computer 20 through input devices
such as a
keyboard 40 and pointing device 42. Other input devices (not shown) may
include a microphone,
joystick, game pad, satellite disk, scanner or the like. These and other input
devices are often
connected to the processing unit 21 through a serial port interface 46 that is
coupled to the
system bus, but may be connected by other interfaces, such as a parallel port,
game port or
universal serial bus (USB). A monitor 47 or other type of display device is
also connected to the
system bus 23 via an interface, such as a video adapter 48. In addition to the
monitor 47,
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personal computers typically include other peripheral output devices (not
shown), such as
speakers and printers. The exemplary system of Fig. 1 also includes a host
adapter 55, Small
Computer System Interface (SCSI) bus 56, and an external storage device 62
connected to the
SCSI bus 56.
[0076] The personal computer 20 may operate in a networked environment using
logical connections to one or more remote computers, such as a remote computer
49. The remote
computer 49 may be another personal computer, a server, a router, a network
PC, a peer device
or other common network node, and typically includes many or all of the
elements described
above relative to the personal computer 20, although only a memory storage
device 50 has been
illustrated in Fig. 1. The logical connections depicted in Fig. 1 include a
local area network
(LAN) 51 and a wide area network (WAN) 52. Such networking environments are
commonplace
in offices, enterprise wide computer networks, intranets and the Internet.
[0077] When used in a LAN networking environment, the personal computer 20 is
connected to the LAN 51 through a network interface or adapter 53. When used
in a WAN
networking environment, the personal computer 20 typically includes a modem 54
or other
means for establishing communications over the wide area network 52, such as
the Internet. The
modem 54, which may be internal or external, is connected to the system bus 23
via the serial
port interface 46. In a networked environment, program modules depicted
relative to the personal
computer 20, or portions thereof, may be stored in the remote memory storage
device. It will be
appreciated that the network connections shown are exemplary and other means
of establishing a
communications link between the computers may be used.
[0078] As illustrated in the block diagram of Fig. 2, a computer system 200
can be
roughly divided into three component groups: the hardware component 202, the
hardware/software interface system component 204, and the applications
programs component
206 (also referred to as the "user component" or "software component" in
certain contexts
herein).
[0079] In various embodiments of a computer system 200, and referring back to
Fig. 1,
the hardware component 202 may comprise the central processing unit (CPU) 21,
the memory
(both ROM 24 and RAM 25), the basic input/output system (BIOS) 26, and various
input/output
(I/O) devices such as a keyboard 40, a mouse 42, a monitor 47, and/or a
printer (not shown),
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among other things. The hardware component 202 comprises the basic physical
infrastructure
for the computer system 200.
[0080] The applications programs component 206 comprises various software
programs
including but not limited to compilers, database systems, word processors,
business programs,
videogames, and so forth. Application programs provide the means by which
computer
resources are utilized to solve problems, provide solutions, and process data
for various users
(machines, other computer systems, and/or end-users).
(0081] The hardware/software interface system component 204 comprises (and, in
some embodiments, may solely consist of) an operating system that itself
comprises, in most
cases, a shell and a kernel. An "operating system" (OS) is a special program
that acts as an
intermediary between application programs and computer hardware. The
hardware/software
interface system component 204 may also comprise a virtual machine manager
(VMM), a
Common Language Runtime (CLR) or its functional equivalent, a Java Virtual
Machine (JVM)
or its functional equivalent, or other such software components in the place
of or in addition to
the operating system in a computer system. The purpose of a hardware/software
interface
system is to provide an environment in which a user can execute application
programs. The goal
of any hardware/software interface system is to make the computer system
convenient to use, as
well as utilize the computer hardware in an efficient manner.
[0082] The hardware/software interface system is generally loaded into a
computer
system at startup and thereafter manages all of the application programs in
the computer system.
The application programs interact with the hardware/software interface system
by requesting
services via an application program interface (API). Some application programs
enable end-
users to interact with the hardware/software interface system via a user
interface such as a
command language or a graphical user interface (GUI).
[0083] A hardware/software interface system traditionally performs a variety
of
services for applications. In a multitasking hardware/software interface
system where multiple
programs may be running at the same time, the hardware/software interface
system determines
which applications should run in what order and how much time should be
allowed for each
application before switching to another application for a turn. The
hardware/software interface
system also manages the sharing of internal memory among multiple
applications, and handles
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input and output to and from attached hardware devices such as hard disks,
printers, and dial-up
ports. The hardware/software interface system also sends messages to each
application (and, in
certain case, to the end-user) regarding the status of operations and any
errors that may have
occurred. The hardware/software interface system can also offload the
management of batch
jobs (e.g., printing) so that the initiating application is freed from this
work and can resume other
processing and/or operations. On computers that can provide parallel
processing, a
hardware/software interface system also manages dividing a program so that it
runs on more than
one processor at a time.
10084] A hardware/software interface system shell (simply referred to herein
as a
"shell") is an interactive end-user interface to a hardware/software interface
system. (A shell
may also be referred to as a "command interpreter" or, in an operating system,
as an "operating
system shell"). A shell is the outer layer of a hardware/software interface
system that is directly
accessible by application programs and/or end-users. In contrast to a shell, a
kernel is a
hardware/software interface system's innermost layer that interacts directly
with the hardware
components.
[0085] While it is envisioned that numerous embodiments of the present
invention are
particularly well-suited for computerized systems, nothing in this document is
intended to limit
the invention to such embodiments. On the contrary, as used herein the term
"computer system"
is intended to encompass any and all devices capable of storing and processing
information
and/or capable of using the stored information to control the behavior or
execution of the device
itself, regardless of whether such devices are electronic, mechanical,
logical, or virtual in nature.
B. TRADITIONAL FILE-BASED STORAGE
[0086] In most computer systems today, "files" are units of storable
information that
may include the hardware/software interface system as well as application
programs, data sets,
and so forth. In all modern hardware/software interface systems (Windows,
Unix, Linux, Mac
OS, virtual machine systems, and so forth), files are the basic discrete
(storable and retrievable)
units of information (e.g., data, programs, and so forth) that can be
manipulated by the
hardware/software interface system. Groups of files are generally organized in
"folders." In
TM TM
Microsoft Windows, the Macintosh OS, and other hardware/software interface
systems, a folder
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is a collection of files that can be retrieved, moved, and otherwise
manipulated as single units of
information. These folders, in turn, are organized in a tree-based
hierarchical arrangement called
a "directory" (discussed in more detail herein below). In certain other
hardware/software
interface systems, such as DOS, z/OS and most Unix-based operating systems,
the terms
TM ,
"directory" and/or "folder" are interchangeable, and early Apple computer
systems (e.g., the
TM
Apple Ile) used the term "catalog" instead of directory; however, as used
herein, all of these
terms are deemed to be synonymous and interchangeable and are intended to
further include all
other equivalent terms for and references to hierarchical information storage
structures and their
folder and file components.
(0087] Traditionally, a directory (a.k.a. a directory of folders) is a tree-
based
hierarchical structure wherein files are grouped into folders and folder, in
turn, are arranged
according to relative nodal locations that comprise the directory tree. For
example, as illustrated
in Fig. 2A, a DOS-based file system base folder (or "root directory") 212 may
comprise a
plurality of folders 214, each of which may further comprise additional
folders (as "subfolders"
of that particular folder) 216, and each of these may also comprise additional
folders 218 ad
infinitum. Each of these folders may have one or more files 220 although, at
the
hardware/software interface system level, the individual files in a folder
have nothing in common
other than their location in the tree hierarchy. Not surprisingly, this
approach of organizing files
into folder hierarchies indirectly reflects the physical organization of
typical storage media used
to store these files (e.g., hard disks, floppy disks, CD-ROMs, etc.).
100881 In addition to the foregoing, each folder is a container for its
subfolders and its
files-that is, each folder owns its subfolders and files. For example, when a
folder is deleted by
the hardware/software interface system, that folder's subfolders and files are
also deleted (which,
in the case of each subfolder, further includes its own subfolders and files
recursively).
Likewise, each file is generally owned by only one folder and, although a file
can be copied and
the copy located in a different folder, a copy of a file is itself a distinct
and separate unit that has
no direct connection to the original (e.g., changes to the original file are
not mirrored in the copy
file at the hardware/software interface system level). In this regard, files
and folders are
therefore characteristically "physical" in nature because folders are the
treated Like physical
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containers, and files are treated as discrete and separate physical elements
inside these
containers.
H. WINFS STORAGE PLATFORM FOR ORGANIZING, SEARCHING, AND
SHARING DATA
[0089] The present invention, in combination with the related inventions
incorporated
by reference as discussed earlier herein, is directed to a storage platform
for organizing,
searching, and sharing data. The storage platform of the present invention
extends and broadens
the data platform beyond the kinds of existing file systems and database
systems discussed
above, and is designed to be the store for all types of data, including a new
form of data called
Items.
A. GLOSSARY
[0090] As used herein and in the claims, the following terms have the
following
meanings:
= An "Item" is an unit of storable information accessible to a
hardware/software
interface system that, unlike a simple file, is an object having a basic set
of
properties that are commonly supported across all objects exposed to an end-
user
by the hardware/software interface system shell. Items also have properties
and
relationships that are commonly supported across all Item types including
features
that allow new properties and relationships to be introduced (and discussed in
great detail later herein).
= An "operating system" (OS) is a special program that acts as an intermediary
between application programs and computer hardware. An operating system
comprises, in most cases, a shell and a kernel.
= A "hardware/software interface system" is software, or a combination of
hardware and software, that serves as the interface between the underlying
hardware components of a computer system and applications that execute on the
computer system. A hardware/software interface system typically comprises
(and, in some embodiments, may solely consist of) an operating system. A
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hardware/software interface system may also comprise a virtual machine manager
(VMM), a Common Language Runtime (CLR) or its functional equivalent, a Java
Virtual Machine (JVM) or its functional equivalent, or other such software
components in the place of or in addition to the operating system in a
computer
system. The purpose of a hardware/software interface system is to provide an
environment in which a user can execute application programs. The goal of any
hardware/software interface system is to make the computer system convenient
to
use, as well as utilize the computer hardware in an efficient manner.
B. STORAGE PLATFORM OVERVIEW
100911 Referring to Fig. 3, a storage platform 300 comprises a data store 302
implemented on a database engine 314. In one-embodiment, the database engine
comprises a
relational database engine with object relational extensions. In one
embodiment, the relational
TM
database engine 314 comprises the Microsoft SQL Server relational database
engine. The data
store 302 implements a data model 304 that supports the organization,
searching, sharing,
synchronization, and security of data. Specific types of data are described in
schemas, such as
schemas 340, and the storage platform 300 provides tools 346 for deploying
those schemas as
well as for extending those schemas, as described more fully below.
10092) A change tracking mechanism 306 implemented within the data store 302
provides the ability track changes to the data store. The data store 302 also
provides security
capabilities 308 and a promotion/demotion capability 310, both of which are
discussed more
fully below. The data store 302 also provides a set of application programming
interfaces 312 to
expose the capabilities of the data store 302 to other storage platform
components and
application programs (e.g., application programs 350a, 350b, and 350c) that
utilize the storage
platform. The storage platform of the present invention still further
comprises an application
programming interfaces (API) 322, which enables application programs, such as
application
programs 350a, 350b, and 350c, to access all of the foregoing capabilities of
the storage platform
and to access the data described in the schemas. The storage platform API 322
may be used by
application programs in combination with other APIs, such as the OLE DB API
324 and the
TM
Microsoft Windows Win32 API 326.
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[0093] The storage platform 300 of the present invention may provide a variety
of
services 328 to application programs, including a synchronization service 330
that facilitates the
sharing of data among users or systems. For example, the synchronization
service 330 may
enable interoperability with other data stores 340 having the same format as
data store 302, as
well as access to data stores 342 having other formats. The storage platform
300 also provides
file system capabilities that allow interoperability of the data store 302
with existing file systems,
such as the Windows NTFS files system 318. In at least some embodiments, the
storage
platform 320 may also provide application programs with additional
capabilities for enabling
data to be acted upon and for enabling interaction with other systems. These
capabilities may be
embodied in the form of additional services 328, such as an Info Agent service
334 and a
notification service 332, as well as in the form of other utilities 336.
[0094] In at least some embodiments, the storage platform is embodied in, or
forms an
integral part of, the hardware/software interface system of a computer system.
For example, and
without limitation, the storage platform of the present invention may be
embodied in, or form an
integral part of, an operating system, a virtual machine manager (VMM), a
Common Language
Runtime (CLR) or its functional equivalent, or a Java Virtual Machine (JVM) or
its functional
equivalent. Through its common storage foundation, and schematized data, the
storage platform
of the present invention enables more efficient application development for
consumers,
knowledge workers and enterprises. It offers a rich and extensible programming
surface area
that not only makes available the capabilities inherent in its data model, but
also embraces and
extends existing file system and database access methods.
[0095] In the following description, and in various ones of the figures, the
storage
platform 300 of the present invention may be referred to as "WinFS." However,
use of this
name to refer to the storage platform is solely for convenience of description
and is not intended
to be limiting in any way.
C. THE DATA MODEL
[0096] The data store 302 of the storage platform 300 of the present invention
implements a data model that supports the organization, searching, sharing,
synchronization, and
security of data that resides in the store. In the data model of the present
invention, an "Item" is
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the fundamental unit of storage information. The data model provides a
mechanism for
declaring Items and Item extensions and for establishing relationships between
Items and for
organizing Items in Item Folders and in Categories, as described more fully
below.
[0097] The data model relies on two primitive mechanisms, Types and
Relationships.
Types are structures which provide a format which governs the form of an
instance of the Type.
The format is expressed as an ordered set of Properties. A Property is a name
for a value or set of
values of a given Type. For example a USPostalAddress type might have the
properties Street,
City, Zip, State in which Street, City and State are of type String and Zip is
of Type Int32. Street
may be multi-valued (i.e. a set of values) allowing the address to have more
than one value for
the Street property. The system defines certain primitive types that can be
used in the
construction of other types - these include String, Binary, Boolean, Intl 6,
Int32, Int64, Single,
Double, Byte, DateTime, Decimal and GUID. The Properties of a Type may be
defined using
any of the primitive types or (with some restrictions noted below) any of the
constructed types.
For example a Location Type might be defined that had Properties Coordinate
and Address
where the Address Property is of Type USPostalAddress as described above.
Properties may also
be required or optional.
[0098] Relationships can be declared and represent a mapping between the sets
of
instances of two types. For example there may be a Relationship declared
between the Person
Type and the Location Type called LivesAt which defines which people live at
which locations.
The Relationship has a name, two endpoints, namely a source endpoint and a
target endpoint.
Relationships may also have an ordered set of properties. Both the Source and
Target endpoints
have a Name and a Type. For example the LivesAt Relationship has a Source
called Occupant of
Type Person and a Target called Dwelling of Type Location and in addition has
properties
StartDate and EndDate indicating the period of time for which the occupant
lived at the dwelling.
Note that a Person may live at multiple dwellings over time and a dwelling may
have multiple
occupants so the most likely place to put the StartDate and EndDate
information is on the
relationship itself.
[0099] Relationships define a mapping between instances that is constrained by
the
types given as the endpoint types. For example the LivesAt relationship cannot
be a relationship
in which an Automobile is the Occupant because an Automobile is not a Person.
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[0100] The data model does allow the definition of a subtype-supertype
relationship
between types. The subtype-supertype relationship also known as the BaseType
relationship is
defined in such a way that if Type A is a BaseType for Type B it must be the
case that every
instance of B is also an instance of A. Another way of expressing this is that
every instance that
conforms to B must also conform to A. If, for example A has a property Name of
Type String
while B has a property Age of Type Intl6, it follows that any instance of B
must have both a
Name and an Age. The type hierarchy may be envisaged as an tree with a single
supertype at the
root. The branches from the root provide the first level subtypes, the
branches at this level
provide the second level subtypes and so on to the leaf-most subtypes which
themselves do not
have any subtypes. The tree is not constrained to be of a uniform depth but
cannot contain any
cycles. A given Type may have zero or many subtypes and zero or one super
type. A given
instance may conform to at most one type together with that type's super
types. To put it another
way, for a given instance at any level in the tree the instance may conform to
at most one subtype
at that level. A type is said to be Abstract if instances of the type must
also be an instance of a
subtype of the type.
1. Items
[0101] An Item is a unit of storable information that, unlike a simple file,
is an object
having a basic set of properties that are commonly supported across all
objects exposed to an
end-user or application program by the storage platform. Items also have
properties and
relationships that are commonly supported across all Item types including
features that allow
new properties and relationships to be introduced, as discussed below.
[0102] Items are the objects for common operations such as copy, delete, move,
open,
print, backup, restore, replicate, and so forth. Items are the units that can
be stored and retrieved,
and all forms of storable information manipulated by the storage platform
exist as Items,
properties of Items, or Relationships between Items, each of which is
discussed in greater detail
herein below.
[0103] Items are intended to represent real-world and readily-understandable
units of
data like Contacts, People, Services, Locations, Documents (of all various
sorts), and so on. Fig.
5A is a block diagram illustrating the structure of an Item. The unqualified
name of the Item is
"Location". The qualified name of the Item is "Core.Location" which indicates
that this Item
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structure is defined as a specific type of Item in the Core Schema. (The Core
Schema is
discussed in more detail later herein.)
[0104] The Location Item has a plurality of properties including EAddresses,
MetropolitanRegion, Neighborhood, and PostalAddresses. The specific type of
property for each
is indicated immediately following the property name and is separated from the
property name
by a colon (":"). To the right of the type name, the number of values
permitted for that property
type is indicated between brackets ("[ ]") wherein an asterisk ("*") to the
right of the colon (":")
indicates an unspecified and/or unlimited number ("many"). A "1" to the right
of the colon
indicates that there can be at most one value. A zero ("0") to the left of the
colon indicates that
the property is optional (there may be no value at all). A "1" to the left of
the colon indicates
that there must be at least one value (the property is required). Neighborhood
and
MetropolitanRegion are both of type "nvarchar" (or equivalent) which is a
predefined data type
or "simple type" (and denoted herein by the lack of capitalization).
EAddresses and
PostalAddresses, however, are properties of defined types or "complex types"
(as denoted herein
by capitalization) of types EAddress and PostalAddress respectively. A complex
type is type
that is derived from one or more simple data types and/or from other complex
types. The
complex types for the properties of an Item also constitute "nested elements"
since the details of
the complex type are nested into the immediate Item to define its properties,
and the information
pertaining to these complex types is maintained with the Item that has these
properties (within
the Item's boundary, as discussed later herein). These concepts of typing are
well known and
readily appreciated by those of skill in the art.
[0105] Fig. 5B is a block diagram illustrating the complex property types
PostalAddress
and EAddress. The PostalAddress property type defines that an Item of property
type
PostalAddress can be expected to have zero or one City values, zero or one
CountryCode values,
zero or one MailStop values, and any number (zero to many) of
PostalAddressTypes, and so on
and so forth. In this way, the shape of the data for a particular property in
an Item is hereby
defined. The EAddress property type is similarly defined as shown. Although
optionally used
herein this Application, another way to represent the complex types in the
Location Item is to
draw the Item with the individual properties of each complex type listed
therein. Fig. 5C is a
block diagram illustrating the Location Item wherein its complex types are
further described.
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However, it should be understood that this alternative representation of the
Location Item in this
Fig. 5C is for the exact same Item illustrated in Fig. 5A. The storage
platform of the present
invention also allows subtyping whereby one property type can be a subtype of
another (where
the one property type inherits the properties of another, parent property
type).
[0106] Similar to but distinct from properties and their property types, Items
inherently
represent their own Item Types that can also be the subject of subtyping. In
other words, the
storage platform in several embodiments of the present invention allows an
Item to be a subtype
of another Item (whereby the one Item inherits the properties of the other,
parent Item).
Moreover, for various embodiments of the present invention, every Item is a
subtype of the
"Item" Item type which is the first and foundational Item type found in the
Base Schema. (The
Base Schema will also be discussed in detail later herein.) Fig. 6A
illustrates an Item, the
Location Item in this Instance, as being a subtype of the Item Item type found
in the Base
Schema. In this drawing, the arrow indicates that the Location Item (like all
other Items) is a
subtype of the Item Item type. The Item Item type, as the foundational Item
from which all other
Items are derived, has a number of important properties such as Itemld and
various timestamps,
and thereby defines the standard properties of all Items in an operating
system. In the present
figure, these properties of the Item Item type are inherited by Location and
thereby become
properties of Location.
[0107] Another way to represent the properties in the Location Item inherited
from the
Item Item type is to draw Location with the individual properties of each
property type from the
parent Item listed therein. Fig. 6B is a block diagram illustrating the
Location Item wherein its
inherited types described in addition to its immediate properties. It should
be noted and
understood that this Item is the same Item illustrated in Fig. 5A, although in
the present figure
Location is illustrated with all of its properties, both immediate-shown in
both this figure and
Fig. 5A-and inherited-shown in this figure but not Fig. 5A (whereas in Fig. 5A
these
properties are referenced by showing with an arrow that the Location Item is a
subtype of the
Item Item type).
[0108] Items are stand-alone objects; thus, if you delete an Item, all of the
Items
immediate and inherited properties are also deleted. Similarly, when
retrieving an Item, what is
received is the Item and all of its immediate and inherited properties
(including the information
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pertaining to its complex property types). Certain embodiments of the present
invention may
enable one to request a subset of properties when retrieving a specific Item;
however, the default
for many such embodiments is to provide the Item with all of its immediate and
inherited
properties when retrieved. Moreover, the properties of Items can also be
extended by adding
new properties to the existing properties of that Item's type. These
"extensions" are thereafter
bona fide properties of the Item and subtypes of that Item type may
automatically include the
extension properties.
[0109] The "boundary" of the Item is represented by its properties (including
complex
property types, extensions, and so forth). An Item's boundary also represents
the limit of an
operation performed on an Item such as copy, delete, move, create, and so on.
For example, in
several embodiments of the present invention, when an Item is copied,
everything within that
Item's boundary is also copied. For each Item, the boundary encompasses the
following:
= The Item Type of the Item and, if the Item is a subtype of another Item (as
is
the case in several embodiments of the present invention where all Items are
derived from a single Item and Item Type in the Base Schema), any applicable
subtype information (that is, information pertaining to the parent Item Type).
If
the original Item being copied is a subtype of another Item, the copy may also
be
a subtype of that same Item.
= The Item's complex-type properties and extensions, if any. If the original
Item has properties of complex types (native or extended), the copy may also
have
the same complex types.
= The Item's records on "ownership relationships", that is, the Item's own
list of
what other Items (the "Target Items") are owned by the present Item (the
"Owning Item"). This is particularly relevant in regard to Item Folders,
discussed
more fully below, and the rule stated below that all Items must belong to at
least
one Item Folder. Moreover, in regard to embedded items-discussed more fully
below-an embedded item is considered to be part of the Item in which it is
embedded for operations such as copy, delete, and the like.
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2. Item Identification
[0110] Items are uniquely identified within the global items space with an
ItemID. The
Base.Item type defines a field ItemID of type GUID that stores the identity
for the Item. An Item
must have exactly one identity in the data store 302.
[0111] An item reference is a data structure that contains information to
locate and
identify an Item. In the data model, an abstract type is defined named
ItemReference from which
all item reference types derive. The ItemReference type defines a virtual
method named Resolve.
The Resolve method resolves the ItemReference and returns an Item. This method
is overridden
by the concrete subtypes of IteniReference, which implement a function that
retrieves an Item
given a reference. The Resolve method is invoked as part of the storage
platform API 322.
[0112] ItemIDReference is a subtype of ItemReference. It defines a Locator and
an
ItemID field. The Locator field names (i.e. identifies) an item domain. It is
processed by a
locator resolution method that can resolve the value of the Locator to an item
domain. The
ItemID field is of type ItemID
[0113] ItemPathReference is a specialization of ItemReference that defines a
Locator
and a Path field. The Locator field identifies an item domain. It is processed
by a locator
resolution method that can resolve the value of the Locator to an item domain.
The Path field
contains a (relative) path in the storage platform namespace rooted at the
item domain provided
by the Locator.
[0114] This type of reference cannot be used in a set operation. The reference
must
generally be resolved through a path resolution process. The Resolve method of
the storage
platform API 322 provides this functionality.
[0115] The reference forms discussed above are represented through the
reference type
hierarchy illustrated in Fig. 11. Additional reference types that inherit from
these types can be
defined in the schemas. They can be used in a relationship declaration as type
of the target field.
3. Item Folders and Categories
[0116] As discussed more fully below, groups of Items can are organized into
special
Items called Item Folders (which are not to be confused with file folders).
Unlike in most file
systems, however, an Item can belong to more than one Item Folder, such that
when an Item is
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accessed in one Item Folder and revised, this revised Item can then be
accessed directly from
another Item folder. In essence, although access to an Item may occur from
different Item
Folders, what is actually being accessed is in fact the very same Item.
However, an Item Folder
does not necessarily own all of its member Items, or may simply co-own Items
in conjunction
with other folders, such that the deletion of an Item Folder does not
necessarily result in the
deletion of the Item. Nevertheless, in several embodiments of the present
invention, an Item
must belong to at least one Item Folder so that if the sole Item Folder for a
particular Item is
deleted then, for some embodiments, the Item is automatically deleted or, in
alternative
embodiments, the Item automatically becomes a member of a default Item Folder
(e.g., a "Trash
Can" Item Folder conceptually similar to similarly-named folders used in
various file-and-folder-
based systems).
[0117] As also discussed more fully below, Items may also belong to Categories
based
on common described characteristic such as (a) an Item Type (or Types), (b) a
specific
immediate or inherited property (or properties), or (c) a specific value (or
values) corresponding
to an Item property. For example, a Item comprising specific properties for
personal contact
information might automatically belong to a Contact Category, and any Item
having contact
information properties would likewise automatically belong to this Category.
Likewise, any
Item having a location property with a value of "New York City" might
automatically belong to
a NewYorkCity Category.
[0118] Categories are conceptually different form Item Folders in that,
whereas Item
Folders may comprise Items that are not interrelated (i.e., without a common
described
characteristic), each Item in a Category has a common type, property, or value
(a
"commonality") that is described for that Category, and it is this commonality
that forms the
basis for its relationship to and among the other Items in the Category.
Moreover, whereas an
Item's membership in a particular Folder is not compulsory based on any
particular aspect of that
Item, for certain embodiments all Items having a commonality categorically
related to a
Category might automatically become a member of the Category at the
hardware/software
interface system level. Conceptually, Categories can also be thought of as
virtual Item Folders
whose membership is based on the results of a specific query (such as in the
context of a
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database), and Items that meet the conditions of this query (defined by the
commonalities of the
Category) would thus comprise the Category's membership.
[0119] Fig. 4 illustrates the structural relationship between Items, Item
Folders, and
Categories. A plurality of Items 402, 404, 406, 408, 410, 412, 414, 416, 418,
and 420 are
members of various Item Folders 422, 424, 426, 428, and 430. Some Items may
belong to more
than one Item Folder, e.g., Item 402 belong to Item Folders 422 and 424. Some
Items, e.g., Item
402, 404, 406, 408, 410, and 412 are also members of one or more Categories
432, 434, and 436,
while other times, e.g., Items 414, 416, 418, and 420, may belong to no
Categories (although this
is largely unlikely in certain embodiments where the possession of any
property automatically
implies membership in a Category, and thus an Item would have to be completely
featureless in
order not to be a member of any category in such an embodiment). In contrast
to the hierarchical
structure of folders, both Categories and Item Folders have structures more
akin to directed
graphs as shown. In any event, the Items, Item Folders, and Categories are all
Items (albeit of
different Item Types).
[0120] In contrast to files, folders, and directories, the Items, Item
Folders, and
Categories of the present invention are not characteristically "physical" in
nature because they do
not have conceptual equivalents of physical containers, and therefore Items
may exist in more
than one such location. The ability for Items to exist in more than one Item
Folder location as
well as being organized into Categories provides an enhanced and enriched
degree of data
manipulation and storage structure capabilities at the hardware/software
interface level, beyond
that currently available in the art.
4. Schemas
a) Base Schema
[0121] To provide a universal foundation for the creation and use of Items,
various
embodiments of the storage platform of the present invention comprise a Base
Schema that
establishes a conceptual framework for creating and organizing Items and
properties. The Base
Schema defines certain special types of Items and properties, and the features
of these special
foundational types from which subtypes can be further derived. The use of this
Base Schema
allows a programmer to conceptually distinguish Items (and their respective
types) from
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properties (and their respective types). Moreover, the Base Schema sets forth
the foundational
set of properties that all Items may possess as all Items (and their
corresponding Item Types) are
derived from this foundational Item in the Base Schema (and its corresponding
Item Type).
[0122] As illustrated in Fig. 7, and in regard to several embodiments of the
present
invention, the Base Schema defines three top-level types: Item, Extension, and
PropertyBase. As
shown, the Item type is defined by the properties of this foundational "Item"
Item type. In
contrast, the top level property type "PropertyBase" has no predefined
properties and is merely
the anchor from which all other property types are derived and through which
all derived
property types are interrelated (being commonly derived from the single
property type). The
Extension type properties define which Item the extension extends as well as
identification to
distinguish one extension from another as an Item may have multiple
extensions.
[0123] ItemFolder is a subtype of the Item Item type that, in addition to the
properties
inherited from Item, features a Relationship for establishing links to its
members (if any),
whereas both IdentityKey and Property are subtypes of PropertyBase.
CategoryRef, in turn, is a
subtype of IdentityKey.
b) Core Schema
[0124] Various embodiments of the storage platform of the present invention
further
comprise a Core Schema that provides a conceptual framework for top-level
Items type
structures. Fig. 8A is a block diagram illustrating Items in the Core Schema,
and Fig. 8B is a
block diagram illustrating the property types in the Core Schema. The
distinction made between
files with different extensions (*.com, *.exe, *.bat, *.sys, etc.) and other
such criteria in file-and-
folder-based systems is analogous to the function of the Core Schema. In the
Item-based
hardware/software interface system, the Core Schema defines a set of core Item
types that,
directly (by Item type) or indirectly (by Item subtype), characterize all
Items into one or more
Core Schema Item types which the Item-based hardware/software interface system
understands
and can directly process in a predetermined and predictable way. The
predefined Item types
reflect the most common Items in the Item-based hardware/software interface
system and thus a
level of efficiency is gained by the Item-based hardware/software interface
system understanding
these predefined Item types that comprise the Core Schema.
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[0125] In certain embodiments, the Core Schema is not extendable-that is, no
additional Item types can be subtyped directly from the Item type in the Base
Schema except for
the specific predefined derived Item types that are part of the Core Schema.
By preventing
extensions to the Core Schema (that is, by preventing the addition of new
Items to the Core
Schema), the storage platform mandates the use of the Core Schema Item types
since every
subsequent Item type is necessarily a subtype of a Core Schema Item type. This
structure
enables a reasonable degree of flexibility in defining additional Item types
while also preserving
the benefits of having a predefined set of core Item types.
[01261 For various embodiments of the present invention, and in reference to
Fig. 8A,
the specific Item types supported by the Core Schema may include one or more
of the following:
= Categories: Items of this Item Type (and subtypes derived therefrom)
represent
valid Categories in the Item-based hardware/software interface system.
= Commodities: Items that are identifiable things of value.
= Devices: Items having a logical structure that supports information
processing
capabilities.
= Documents: Items with content that is not interpreted by the Item-based
hardware/software interface system but is instead interpreted by an
application
program corresponding to the document type.
= Events: Items that record certain occurrences in the environment.
= Locations: Items representing physical locations (e.g., geographical
locations).
= Messages: Items of communication between two or more principals (defined
below).
= Principals: Items having at least one definitively provable identity aside
from an
Itemld (e.g., the identification of a person, organization, group, household,
authority, service, etc.).
= Statements: Items having special information regarding the environment
including, without limitation, policies, subscriptions, credentials, and so
forth.
[01271 Likewise, and in reference to Fig. 8B, the specific property types
supported by
the Core Schema may include one or more of the following:
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= Certificates (derived from the foundational PropertyBase type in the Base
Schema)
= Principal Identity Keys (derived from the IdentityKey type in the Base
Schema)
= Postal Address (derived from the Property type in the Base Schema)
= Rich Text (derived from the Property type in the Base Schema)
= EAddress (derived from the Property type in the Base Schema)
= IdentitySecurityPackage (derived from the Relationship type in the Base
Schema)
= RoleOccupancy (derived from the Relationship type in the Base Schema)
= BasicPresence (derived from the Relationship type in the Base Schema)
These Items and Properties are further described by their respective
properties set forth in Fig.
8A and Fig. 8B.
5. Relationships
[0128] Relationships are binary relationships where one Item is designated as
source
and the other Item as target. The source Item and the target Item are related
by the relationship.
The source Item generally controls the life-time of the relationship. That is,
when the source Item
is deleted, the relationship between the Items is also deleted.
[0129] Relationships are classified into: Containment and Reference
relationships. The
containment relationships control the life-time of the target Items, while the
reference
relationships do not provide any life-time management semantics. Fig. 12
illustrates the manner
in which relationships are classified.
[0130] The Containment relationship types are further classified into Holding
and
Embedding relationships. When all holding relationships to an Item are
removed, the Item is
deleted. A holding relationship controls the life-time of the target through a
reference counting
mechanism. The embedding relationships enable modeling of compound Items and
can be
thought of as exclusive holding relationships. An Item can be a target of one
or more holding
relationships; but an Item can be target of exactly one embedding
relationship. An Item that is a
target of an embedding relationship can not be a target of any other holding
or embedding
relationships.
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[0131] Reference relationships do not control the lifetime of the target Item.
They may
be dangling - the target Item may not exist. Reference relationships can be
used to model
references to Items anywhere in the global Item name space (i.e. including
remote data stores).
[0132] Fetching an Item does not automatically fetch its relationships.
Applications
must explicitly request the relationships of an Item. In addition, modifying a
relationship does
not modify the source or the target Item; similarly, adding a relationship
does not affect the
source/target Item.
a) Relationship Declaration
[0133] The explicit relationship types are defined with the following
elements:
= A relationship name is specified in the Name attribute.
= Relationship type, one of the following: Holding, Embedding, Reference. This
is
specified in the Type attribute.
= Source and target endpoints. Each endpoint specifies a name and the type of
the
referenced Item.
= The source endpoint field is generally of type ItemID (not declared) and it
must
reference an Item in the same data store as the relationship instance.
= For Holding and Embedding relationships, the target endpoint field must be
of
type ItemlDReference and it must reference an Item in the same store as the
relationship instance. For Reference relationships the target endpoint can be
of
any ItemReference type and can reference Items in other storage platform data
stores.
= Optionally one or more fields of a scalar or PropertyBase type can be
declared.
These fields may contain data associated with the relationship.
= Relationship instances are stored in a global relationships table.
= Every relationship instance is uniquely identified by the combination
(source
ItemID, relationship ID). The relationship ID is unique within a given source
ItemID for all relationships sourced in a given Item regardless of their type.
[0134] The source Item is the owner of the relationship. While an Item
designated as
owner controls the life time of the relationship, the relationship itself is
separate from the Items it
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relates. The storage platform API 322 provides mechanisms for exposing
relationships associated
with an Item.
[0135] Here is an example of a relationship declaration:
<Relationship Name="Employment" BaseType="Reference" >
<Source Name="Employee" ItemType="Contact.Person"/>
<Target Name="Employer" ItemType=" Contact. Organization"
ReferenceType="ItemlDReference" />
<Property Name=" StartD ate" Type="the storage
platformTypes.DateTime" />
<Property Name="EndDate" Type="the storage
platformTypes.DateTime" />
<Property Name="Office" Type="the storage
platformTypes.DateTime" />
</Relationship>
[0136] This is an example of a Reference relationship. The relationship can
not be
created if the person Item that is referenced by the source reference does not
exist. Also, if the
person Item is deleted, the relationship instances between the person and
organization are
deleted. However, if the Organization Item is deleted, the relationship is not
deleted and it is
dangling.
b) Holding Relationship
[0137] Holding relationships are used to model reference count based life-time
management of the target Items.
[0138] An Item can be a source endpoint for zero or more relationships to
Items. An
Item that is not an embedded Item can be a target of in one or more holding
relationships.
[0139] The target endpoint reference type must be ItemlDReference and it must
reference an Item in the same store as the relationship instance.
[0140] Holding relationships enforce lifetime management of the target
endpoint. The
creation of a holding relationship instance and the Item that it is targeting
is an atomic operation.
Additional holding relationship instances can be created that are targeting
the same Item. When
the last holding relationship instance with a given Item as target endpoint is
deleted the target
Item is also deleted.
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[0141] The types of the endpoint Items specified in the relationship
declaration will
generally be enforced when an instance of the relationship is created. The
types of the endpoint
Items can not be changed after the relationship is established.
[0142] Holding relationships play a key role in forming the Item namespace.
They
contain the "Name" property that defines the name of the target Item relative
to the source Item.
This relative name is unique for all the holding relationships sourced from a
given Item. The
.ordered list of this relative names starting from the root Item to a given
Item forms the full name
to the Item.
[0143] The holding relationships form a directed acyclic graph (DAG). When a
holding
relationship is created the system ensures that a cycle is not created, thus
ensuring that the Item
namespace forms a DAG.
[0144] While the holding relationship controls the life time of the target
Item, it does
not control the operational consistency of the target endpoint Item. The
target Item is
operationally independent from the Item that owns it through a holding
relationship. Copy,
Move, Backup and other operations on an Item that is a source of a holding
relationship do not
affect the Item that is a target of the same relationship - for example that
is, backing up a Folder
Item does not automatically backup all the Items in the folder (targets of the
FolderMember
relationship).
[0145] The following is an example of a holding relationship:
<Relationship Name="FolderMembers" BaseType="Holding" >
<Source Name="Folder" ItemType="Base.Folder"/>
<Target Name="Item" ItemType="Base.Item"
ReferenceType="ItemlDReference" />
</Relationship>
[0146] The FolderMembers relationship enables the concept of a Folder as a
generic
collection of Items.
c) Embedding Relationships
[0147] Embedding relationships model the concept of exclusive control of the
lifetime
of the target Item. They enable the concept of compound Items.
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[0148] The creation of an embedding relationship instance and the Item that it
is
targeting is an atomic operation. An Item can be a source of zero or more
embedding
relationship. However, an Item can be a target of one and only one embedding
relationship. An
Item that is a target of an embedding relationship can not be a target of a
holding relationship.
[0149] The target endpoint reference type must be ItemlDReference and it must
reference an Item in the same data store as the relationship instance.
[0150] The types of the endpoint Items specified in the relationship
declaration will
generally be enforced when an instance of the relationship is created. The
types of the endpoint
Items can not be changed after the relationship is established.
[0151] Embedding relationships control the operational consistency of the
target
endpoint. For example the operation of serializing of an Item may include
serialization of all the
embedding relationships that source from that Item as well as all of their
targets; copying an Item
also copies all its embedded Items.
[0152] The following is an example declaration:
<Relationship Name="ArchiveMembers" BaseType="Embedding" >
<Source Name="Archive" ItemType="Zip.Archive" 1>
<Target Name="Member" ItemType="Base.Item
ReferenceType="ItemIDReference" />
<Property Name="ZipSize" Type="the storage
platformTypes.bigint" 1>
<Property Name="SizeReduction" Type="the storage
platformTypes.float" />
</Relationship>
d) Reference Relationships
[0153] The reference relationship does not control life time of the Item it
references.
Even more, the reference relationships do not guarantee the existence of the
target, nor do they
guarantee the type of the target as specified in the relationship declaration.
This means that the
reference relationships can be dangling. Also, the reference relationship can
reference Items in
other data stores. Reference relationships can be thought of as a concept
similar to links in web
pages.
[0154] An example of reference relationship declaration is the following:
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<Relationship Name="DocumentAuthor" BaseType="Reference" >
<Sourc ItemType="Document"
ItemType="Base.Document"/>
<Target ItemType="Author" ItemType="Base.Author"
ReferenceType="ItemlDReference" 1>
<Property Type="Role" Type=" Core.CategoryRef' />
<Property Type="DisplayName" Type="the storage
platformTypes.nvarchar(256)" />
</Relationship>
[0155] Any reference type is allowed in the target endpoint. The Items that
participate
in a reference relationship can be of any Item type.
[0156] Reference relationships are used to model most non-lifetime management
relationships between Items. Since the existence of the target is not
enforced, the reference
relationship is convenient to model loosely-coupled relationships. The
reference relationship can
be used to target Items in other data stores including stores on other
computers.
e) Rules and Constraints
[0157] The following additional rules and constraints apply for relationships:
= An Item must be a target of (exactly one embedding relationship) or (one or
more
holding relationships). One exception is the root Item. An Item can be a
target of
zero or more reference relationships
= An Item that is a target of embedding relationship can not be source of
holding
relationships. It can be a source of reference relationships.
= An Item can not be a source of holding relationship if it is promoted from
file. It
can be a source of embedding relationships and reference relationships.
= An Item can that is promoted from a file can not be a target of an embedding
relationship.
f) Ordering of Relationships
[0158] In at least one embodiment, the storage platform of the present
invention
supports ordering of relationships. The ordering is achieved through a
property named "Order" in
the base relationship definition. There is no uniqueness constraint on the
Order field. The order
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of the relationships with the same "order" property value is not guaranteed,
however it is
guaranteed that they may be ordered after relationships with lower "order"
value and before
relationships with higher "order" field value.
[0159] Applications can get the relationships in the default order by ordering
on the
combination ( SourceItemID, RelationshiplD, Order). All relationship instances
sourced from a
given Item are ordered as a single collection regardless of the type of the
relationships in the
collection. This however guarantees that all relationships of a given type
(e.g., FolderMembers)
are an ordered subset of the relationship collection for a given Item.
[0160] The data store API 312 for manipulating relationships implement a set
of
operations that support ordering of relationships. The following terms are
introduced to help
explain the operations:
= RelFirst is the first relationship in the ordered collection with order
value
OrdFirst;
= RelLast is the last relationship in the ordered collection with order value
OrdLast;
= Re1X is a given relationship in the collection with order value OrdX;
= RelPrev is a closest relationship in the collection to RelX with order value
OrdPrev smaller then OrdX; and
= RelNext is a closest relationship in the collection to Re1X with order value
OrdNext greater then OrdX
[0161] The operations include but are not limited to:
= InsertBeforeFirst(SourceltemlD, Relationship) inserts the relationship as
the first
relationship in the collection. The value of the "Order" property of the new
relationship may be smaller then OrdFirst.
= InsertAfterLast(SourceltemlD, Relationship) inserts the relationship as the
last
relationship in the collection. The value of the "Order" property of the new
relationship may be greater then OrdLast.
= InsertAt( SourceltemlD, ord, Relationship) inserts a relationship with the
specified value for the "Order" property.
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= InsertBefore(SourceltemlD, ord, Relationship) inserts the relationship
before the
relationship with the given order value. The new relationship may be assigned
"Order" value that is between OrdPrev and ord, noninclusive.
= InsertAfter(SourceltemlD, ord, Relationship) inserts the relationship after
the
relationship with the given order value. The new relationship may be assigned
"Order" value that is between ord and OrdNext, non-inclusive.
= MoveBefore(SourceltemlD, ord, RelationshiplD) moves the relationship with
given relationship ID before the relationship with specified "Order" value.
The
relationship may be assigned a new "Order" value that is between OrdPrev and
ord, non-inclusive.
= MoveAfter(SourceltemlD, ord, RelationshiplD) moves the relationship with
given relationship ID after the relationship with specified "Order" value. The
relationship may be assigned a new order value that is between ord and
OrdNext,
non-inclusive.
[0162] As previously mentioned, every Item must be a member of an Item Folder.
In
terms of Relationships, every Item must have a relationship with an Item
Folder. In several
embodiments of the present invention, certain relationships are represented by
Relationships
existing between the Items.
[0163] As implemented for various embodiments of the present invention, a
Relationship provides a directed binary relationship that is "extended" by one
Item (the source)
to another Item (the target). A Relationship is owned by the source Item (the
Item that extended
it), and thus the Relationship is removed if the source is removed (e.g., the
Relationship is
deleted when the source Item is deleted). Moreover, in certain instances, a
Relationship may
share ownership of (co-own) the target Item, and such ownership might be
reflected in the
IsOwned property (or its equivalent) of the Relationship (as shown in Fig. 7
for the Relationship
property type). In these embodiments, creation of a new IsOwned Relationship
automatically
increments a reference count on the target Item, and deletion of such a
Relationship may
decrement the reference count on the target Item. For these specific
embodiments, Items
continue to exist if they have a reference count greater than zero, and are
automatically deleted if
and when the count reaches zero. Again, an Item Folder is an Item that has (or
is capable of
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having) a set of Relationships to other Items, these other Items comprising
the membership of the
Item Folder. Other actual implementations of Relationships are possible and
anticipated by the
present invention to achieve the functionality described herein.
[01641 Regardless of actual implementation, a Relationship is a selectable
connection
from one object to another. The ability for an Item to belong to more than one
Item Folder, as
well as to one or more Categories, and whether these Items, Folders, and
Categories are public or
private, is determined by the meanings given to the existence (or lack
thereof) in an Item-based
structure. These logical Relationships are the meanings assigned to a set of
Relationships,
regardless of physical implementation, which are specifically employed to
achieve the
functionality described herein. Logical Relationships are established between
the Item and its
Item Folder(s) or Categories (and vice versa) because, in essence, Item
Folders and Categories
are each a special type of Item. Consequently, Item Folders and Categories can
be acted upon
the same way as any other Item-copied, added to an email message, embedded in
a document,
and so and so forth without limitation-and Item Folders and Categories can be
serialized and
de-serialized (imported and exported) using the same mechanisms as for other
Items. (For
example, in XML all Items might have a serialization format, and this format
applies equally to
Item Folders, Categories, and Items.)
[0165] The aforementioned Relationships, which represent the relationship
between an
Item and it Item Folder(s) can logically extend from the Item to the Item
Folder, from the Item
Folder to the Item, or both. A Relationship that logically extends from an
Item to an Item Folder
denotes that the Item Folder is public to that Item and shares its membership
information with
that Item; conversely, the lack of a logical Relationship from an Item to an
Item Folder denotes
that the Item Folder is private to that Item and does not share its membership
information with
that Item. Similarly, a Relationship that logically extends from an Item
Folder to an Item
denotes that the Item is public and sharable to that Item Folder, whereas the
lack of a logical
Relationship from the Item Folder to the Item denotes that the Item is private
and non-sharable.
Consequently, when an Item Folder is exported to another system, it is the
"public" Items that
are shared in the new context, and when an Item searches its Items Folders for
other, sharable
Items, it is the "public" Item Folders that provide the Item with information
regarding sharable
Items that belong thereto.
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10166] Fig. 9 is a block diagram illustrating an Item Folder (which, again, is
an Item
itself), its member Items, and the interconnecting Relationships between the
Item Folder and its
member Items. The Item Folder 900 has as members a plurality of Items 902,
904, and 906.
Item Folder 900 has a Relationship 912 from itself to Item 902 which denotes
that the Item 902
is public and sharable to Item Folder 900, its members 904 and 906, and any
other Item Folders,
Categories, or Items (not shown) that might access Item Folder 900. However,
there is no
Relationship from Item 902 to the Item Folder 900 which denotes that Item
Folder 900 is private
to Item 902 and does not share its membership information with Item 902. Item
904, on the
other hand, does have a Relationship 924 from itself to Item Folder 900 which
denotes that the
Item Folder 900 is public and shares its membership information with Item 904.
However, there
is no Relationship from the Item Folder 900 to Item 904 which denotes that
Item 904 is private
and not sharable to Item Folder 900, its other members 902 and 906, and any
other Item Folders,
Categories, or Items (not shown) that might access Item Folder 900. In
contrast with its
Relationships (or lack thereof) to Items 902 and 904, Item Folder 900 has a
Relationship 916
from itself to the Item 906 and Item 906 has a Relationship 926 back to Item
Folder 900, which
together denote that Item 906 is public and sharable to Item Folder 900, its
members 902 and
904, and any other Item Folders, Categories, or Items (not shown) that might
access Item Folder
900, and that Item Folder 900 is public and shares its membership information
with Item 906.
[0167] As previously discussed, the Items in an Item Folder do not need to
share a
commonality because Item Folders are not "described." Categories, on the other
hand, are
described by a commonality that is common to all of its member Items.
Consequently the
membership of a Category is inherently limited to Items having the described
commonality and,
in certain embodiments, all Items meeting the description of a Category are
automatically made
members of the Category. Thus, whereas Item Folders allow trivial type
structures to be
represented by their membership, Categories allow membership based on the
defined
commonality.
[0168] Of course Category descriptions are logical in nature, and therefore a
Category
may be described by any logical representation of types, properties, and/or
values. For example,
a logical representation for a Category may be its membership to comprise
Items have one of two
properties or both. If these described properties for the Category are "A" and
"B", then the
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Categories membership may comprise Items having property A but not B, Items
having property
B but not A, and Items having both properties A and B. This logical
representation of properties
is described by the logical operator "OR" where the set of members described
by the Category
are Items having property A OR B. Similar logical operands (including without
limitation
"AND", "XOR", and "NOT" alone or in combination) can also be used describe a
category as
will be appreciated by those of skill in the art.
[0169] Despite the distinction between Item Folders (not described) and
Categories
(described), Categories Relationship to Items and Items Relationship to
Categories essentially
the same way as disclosed herein above for Item Folders and Items in many
embodiments of the
present invention.
[0170] Fig. 10 is a block diagram illustrating a Category (which, again, is an
Item
itself), its member Items, and the interconnecting Relationships between the
Category and its
member Items. The Category 1000 has as members a plurality of Items 1002,
1004, and 1006,
all of which share some combination of common properties, values, or types
1008 as described
(commonality description 1008') by the Category 1000. Category 1000 has a
Relationship 1012
from itself to Item 1002 which denotes that the Item 1002 is public and
sharable to Category
1000, its members 1004 and 1006, and any other Categories, Item Folders, or
Items (not shown)
that might access Category 1000. However, there is no Relationship from the
Item 1002 to the
Category 1000 which denotes that Category 1000 is private to Item 1002 and
does not share its
membership information with Item 1002. Item 1004, on the other hand, does have
a
Relationship 1024 from itself to Category 1000 which denotes that the Category
1000 is public
and shares its membership information with Item 1004. However, there is no
Relationship
extended from Category 1000 to the Item 1004 which denotes that Item 1004 is
private and not
sharable to Category 1000, its other members 1002 and 1006, and any other
Categories, Item
Folders, or Items (not shown) that might access Category 1000. In contrast to
its Relationships
(or lack thereof) with Items 1002 and 1004, Category 1000 has a Relationship
1016 from itself to
Item 1006 and Item 1006 has a Relationship 1026 back to Category 1000, which
altogether
denotes that Item 1006 is public and sharable to Category 1000, its Item
members 1002 and
1004, and any other Categories, Item Folders, or Items (not shown) that might
access Category
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1000, and that the Category 1000 is public and shares its membership
information with Item
1006.
[0171] Finally, because Categories and Item Folders are themselves Items, and
Items
may Relationship to each other, Categories may Relationship to Item Folders
and vice versa, and
Categories, Item Folders, and Items can Relationship to other Categories, Item
Folders, and Item
respectively in certain alternative embodiments. However, in various
embodiments, Item Folder
structures and/or Category structures are prohibited, at the hardware/software
interface system
level, from containing cycles. Where Item Folder and Category structures are
akin to directed
graphs, the embodiments that prohibit cycles are akin to directed acyclic
graphs (DAGs) which,
by mathematical definition in the art of graph theory, are directed graphs
wherein no path starts
and ends at the same vertex.
6. Extensibility
[0172] The storage platform is intended to be provided with an initial set of
schemas
340, as described above. In addition, however, in at least some embodiments,
the storage
platform allows customers, including independent software vendor (ISVs), to
create new
schemas 344 (i.e. new Item and Nested Element types). This section addresses
the mechanism
for creating such schemas by extending the Item types and Nested Element types
(or simply
"Element" types) defined in the initial set of schemas 340.
[0173] Preferably, extension of the initial set of Item and Nested Element
types is
constrained as follows:
= an ISV is allowed to introduce new Item types, i.e. subtype Base.Item;
= an ISV is allowed to introduce new Nested Element types, i.e. subtype
Base.NestedElement;
= an ISV is allowed to introduce new extensions, i.e. subtype
Base.NestedElement;
but,
= an ISV cannot subtype any types (Item, Nested Element, or Extension types)
defined by the initial set of storage platform schemas 340.
[0174] Since an Item type or Nested Element type defined by the initial set of
storage
platform schemas may not exactly match an ISV application's need, it is
necessary to allow ISVs
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to customize the type. This is allowed with the notion of Extensions.
Extensions are strongly
typed instances but (a) they cannot exist independently and (b) they must be
attached to an Item
or Nested Element.
[0175] In addition to addressing the need for schema extensibility, Extensions
are also
intended to address the "multi-typing" issue. Since, in some embodiments, the
storage platform
may not support multiple inheritance or overlapping subtypes, applications can
use Extensions as
a way to model overlapping type instances (e.g. Document is a legal document
as well a secure
document).
a) Item extensions
[0176] To provide Item extensibility, the data model further defines an
abstract type
named Base.Extension. This is a root type for the hierarchy of extension
types. Applications can
subtype Base.Extension to create specific extension types.
[0177] The Base.Extension type is defined in the Base schema as follows:
<Type Name="Base. Extension" IsAbstract="True">
<Propety Name="ItemID"
Type="the storage platformTypes.uniqueidentified"
NuIlable="false"
MultiValued="false"/>
<Property Name="ExtensionlD"
Type="the storage platformTypes.uniqueidentified"
NuIlable="false"
MultiValued="false"/>
</Type>
[0178] The ItemID field contains the ItemID of the item that the extension is
associated
with. An Item with this ItemID must exist. The extension can not be created if
the item with the
given ItemID does not exist. When the Item is deleted all the extensions with
the same ItemID
are deleted. The tuple (ItemID,ExtensionlD) uniquely identifies an extension
instance.
[0179] The structure of an extension type is similar to that of an item type:
= Extension types have fields;
= Fields can be of primitive or nested element types; and
= Extension types can be sub-typed.
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[0180] The following restrictions apply for extension types
= Extensions can not be sources and targets of relationships;
= Extension type instances can not exist independently from an item; and
= Extension types can not be used as field types in the storage platform type
definitions
[0181] There are no constraints on the types of extensions that can be
associated with a
given Item type. Any extension type is allowed to extend any item type. When
multiple
extension instances are attached to an item, they are independent from each
other in both
structure and behavior.
[0182] The extension instances are stored and accessed separately from the
item. All
extension type instances are accessible from a global extension view. An
efficient query can be
composed that will return all the instances of a given type of extension
regardless of what type of
item they are associated with. The storage platform APIs provides a
programming model that can
store, retrieve and modify extensions on items.
[0183] The extension types can be type sub-typed using the storage platform
single
inheritance model. Deriving from an extension type creates a new extension
type. The structure
or the behavior of an extension cannot override or replace the structure or
behaviors of the item
type hierarchy. Similar to Item types, Extension type instances can be
directly accessed through
the view associated with the extension type. The ItemID of the extension
indicates which item
they belong to and can be used to retrieve the corresponding Item object from
the global Item
view. The extensions are considered part of the item for the purposes of
operational consistency.
The Copy/Move, Backup/Restore and other common operations that the storage
platform defines
may operate on the extensions as part of the item.
[0184] Consider the following example. A Contact type is defined in the
Windows
Type set.
<Type Name="Contact" BaseType="Base. Item" >
<Property Name="Name"
Type="String"
Nullable="false"
MultiValued="false"/>
<Property Name="Address"
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Type="Address"
Nullabie="true"
MultiValued="false"/>
</Type>
[0185] A CRM application developer would like to attach a CRM application
extension
to the contacts stored in the storage platform. The application developer
would define a CRM
extension that would contain the additional data structure that the
application can manipulate.
<Type Name="CRMExtension" BaseType="Base. Extension" >
<Property Name="CustomertD"
Type="String"
Nullabie="false"
MultiValued="false"/>
</Type>...
[0186] An HR application developer may want to also attach additional data
with the
Contact. This data is independent from the CRM application data. Again the
application
developer can create an extension
<Type Name="HRExtension" EBaseType="Base. Extension" >
<Property Name="EmployeelD"
Type="String"
Nullabie="false"
MultiValued="false"/>
</Type>...
[0187] CRMExtension and HRExtension are two independent extensions that can be
attached to Contact items. They are created and accessed independently of each
other.
[0188] In the above example, the fields and methods of the CRMExtension type
cannot
override fields or methods of the Contact hierarchy. It should be noted that
instances of the
CRMExtension type can be attached to Item types other than Contact.
[0189] When the Contact item is retrieved, its item extensions are not
automatically
retrieved. Given a Contact item, its related item extensions can be accessed
by querying the
global extension view for extensions with the same Itemld.
[0190] All CRMExtension extensions in the system can be accessed through the
CRMExtension type view, regardless of which item they belong to. All item
extension of an item
share the same item id. In the above example, the Contact item instance and
the attached
CRMExtension and HRExtension instances the same ItemID.
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(0191) The following table summarizes the similarities and differences between
Item,
Extension and NestedElement types:
Item vs Item Extension vs NestedElement
Item Item Extension NestedElement
Item ID Has its own item id Shares the item id Does not have its
of the item own item id. Nested
element is part of
the item
Storage Item hierarchy is Item extension Stored with item
stored in its own hierarchy is stored
tables in its own tables
Query/Search Can query item Can query item Can generally be
tables extension tables queried only within
the containing item
context
Query/Search Can search across Can search across Can generally only
scope all instances of an all instances of an search within nested
item type item extension type element type
instances of a singe
(containing) item
Relationship Can have No Relationships to No Relationships to
semantics Relationships to item extensions nested elements
items
Association to Can be related to Can generally only Related to item via
items other items via be related via fields. Nested
holding, embedded extensions. The elements are part of
and soft extension semantics the item
Relationships is similar to
embedded item
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semantics
b) Extending NestedElement types
[0192] Nested Element types are not extended with the same mechanism as the
Item
types. Extensions of nested elements are stored and accessed with the same
mechanisms as fields
of nested element types.
[0193] The data model defines a root for nested element types named Element:
<Type Name="Element"
IsAbstract="True">
<Property Name="ElementlD"
Type="the storage platformTypes.uniqueidentifier"
Nullable="false"
MultiValued="false"/>
</Type>
[0194] The NestedElement type inherits from this type. The NestedElement
element
type additionally defines a field that is a multi-set of Elements.
<Type Name="Nested Element" BaseType="Base.Element"
IsAbstract="True">
<Property Name="Extensions"
Type="Base. Element"
Nullable="false"
MultiValued="true"/>
</Type>
[0195] The NestedElement extensions are different from item extensions in the
following ways:
= Nested element extensions are not extension types. They do not belong to the
extension type hierarchy that is rooted in the Base.Extension type.
= Nested element extensions are stored along with the other fields of the item
and
are not globally accessible - a query can not be composed that retrieves all
instances of a given extension type.
= These extensions are stored the same way as other nested elements (of the
item)
are stored. Like other nested sets, the NestedElement extensions are stored in
a
UDT. They are accessible through the Extensions field of the nested element
type.
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= The collection interfaces used to access multi-valued properties is also
used for
accessing and iterating over set of type extensions.
[0196] The following table summarizes and compares Item Extensions and
NestedElement extensions.
Item extensions vs NestedElement extensions
Item Extension NestedElement Extension
Storage Item extension hierarchy is Stored like nested elements
stored in its own tables
Query/Search Can query item extension Can generally only be
tables queried within the
containing item context
Query/Search Can search across all Can generally only search
scope instances of an item within nested element type
extension type instances of a singe
(containing) item
Programmability Need special extension NestedElement extensions
APIs and special querying are like any other multi-
on extension tables valued field of nested
element; normal nested
element type APIs are used
Behavior Can associate behavior No behavior permitted (?)
Relationship No Relationships to item No Relationships to
semantics extensions NestedElement extensions
Item ID Shares the item id of the Does not have its own item
item id. NestedElement
extension is part of the
item
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D. DATABASE ENGINE
[01971 As mentioned above, the data store is implemented on a database engine.
In the
present embodiment, the database engine comprises a relational database engine
that implements
TM
the SQL query language, such as the Microsoft SQL Server engine, with object
relational
extensions. This section describes the mapping of the data model that the data
store implements
to the relational store and provides information on the logical API consumed
by storage platform
clients, in accordance with the present embodiment. It is understood, however,
that a different
mapping may be employed when a different database engine is employed. Indeed,
in addition to
implementing the storage platform conceptual data model on a relational
database engine, it can
also be implemented on other types of databases, e.g. object-oriented and XML
databases.
[0198] An object-oriented (OO) database system provides persistence and
transactions
for programming language objects (e.g. C++, Java). The storage platform notion
of an "item"
maps well to an "Object" in object-oriented systems, though embedded
collections would have to
be added to Objects. Other storage platform type concepts, like inheritance
and nested element
types, also map object-oriented type systems. Object-oriented systems
typically already support
object identity; hence, item identity can be mapped to object identity. The
item behaviors
(operations) map well to object methods. However, object-oriented systems
typically lack
organizational capabilities and are poor in searching. Also, object-oriented
systems to do not
provide support for unstructured and semi-structured data. To support the
complete storage
platform data model described herein, concepts like relationships, folders,
and extensions would
need to be added to the object data model. In addition, mechanisms like
promotions,
synchronization, notifications, and security would need to be implemented.
[0199] Similar to object-oriented systems, XML databases, based on XSD (XML
Schema Definition), support a single-inheritance based type system. The item
type system of the
present invention could be mapped to the XSD type model. XSDs also do not
provide support for
behaviors. The XSDs for items would have to be augmented with item behaviors.
XML
databases deal with single XSD documents and lack organization and broad
search capabilities.
As with object-oriented databases, to support the data model described herein,
other concepts
like relationships, and folders would need to be incorporated into such XML
databases; also,
mechanisms like synchronization, notifications and security would need to be
implemented.
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[02001 In regard to the following subsections, a few illustrations are
provided to
facilitate the general information disclosed: Fig. 13 is a diagram
illustrating a notification
mechanism. Fig. 14 is a diagram illustrating an example in which two
transactions are both
inserting a new record into the same B-Tree. Fig. 15 illustrates a data change
detection process.
Fig. 16 illustrates an exemplary directory tree. Fig. 17 shows an example in
which an existing
folder of a directory-based file system is moved into the storage platform
data store.
I. Data Store Implementation Using UDTs
102011 In the present embodiment, the relational database engine 314, which in
one
embodiment comprises the Microsoft SQL Server engine, supports built-in scalar
types. Built-in
scalar types are "native" and "simple". They are native in the sense that the
user cannot define
their own types and they are simple in that they cannot encapsulate a complex
structure. User-
defined types (hereinafter: TJDTs) provide a mechanism for type extensibility
above and beyond
the native scalar type system by enabling users to extend the type system by
defining complex,
structured types. Once defined by a user, a UDT can be used anywhere in the
type system that a
built-in scalar type might be used
[02021 In accordance with an aspect of the present invention, the storage
platform
schemas are mapped to UDT classes in the database engine store. Data store
Items are mapped
to UDT classes deriving from the Base.Item type. Like Items, Extensions are
also mapped to
UDT classes and make use of inheritance. The root Extension type is
Base.Extension, from
which all Extension types are derived.
102031 A LTDT is a CLR class -it has state (i.e., data fields) and behavior
(i.e.,
routines). VDTs are defined using any of the managed languages - C#, VB.NET,
etc. UDT
methods and operators can be invoked in T-SQL against an instance of that
type. A UDT can be:
the type of a column in a row, the type of a parameter of a routine in T-SQL,
or the type of a
variable in T-SQL
[0204] The mapping of storage platform schemas to UDT classes is fairly
straightforward at a high level. Generally, a storage platform Schema is
mapped to a CLR
namespace. A storage platform Type is mapped to a CLR class. The CLR class
inheritance
mirrors the storage platform Type inheritance, and a storage platform Property
is mapped to a
CLR class property.
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2. Item Mapping
[0205] Given the desirability for Items to be globally searchable, and the
support in the
relational database of the present embodiment for inheritance and type
substitutability, one
possible implementation for Item storage in the database store would be to
store all Items in a
single table with a column of type Base.Item. Using type substitutability,
Items of all types
could be stored, and searches could be filtered by Item type and sub-type
using Yukon's "is of
(Type)" operator.
[0206] However, due to concerns about the overhead associated with such an
approach,
in the present embodiment, the Items are divided by top-level type, such that
Items of each type
"family" are stored in a separate table. Under this partitioning scheme, a
table is created for each
Item type inheriting directly from Base.Item. Types inheriting below these are
stored in the
appropriate type family table using type substitutability, as described above.
Only the first level
of inheritance from Base.Item is treated specially.
[0207] A "shadow" table is used to store copies of globally searchable
properties for all
Items. This table may be maintained by the Update() method of the storage
platform API,
through which all data changes are made. Unlike the type family tables, this
global Item table
contains only the top-level scalar properties of the Item, not the full UDT
Item object. The
global Item table allows navigation to the Item object stored in a type family
table by exposing
an ItemID and a TypeID. The ItemID will generally uniquely identify the Item
within the data
store. The TypelD may be mapped using metadata, which is not described here,
to a type name
and the view containing the Item. Since finding an Item by its ItemID may be a
common
operation, both in the context of the global Item table and otherwise, a
Getltem() function is
provided to retrieve an Item object given an Item's ItemID.
[0208] For convenient access and to hide implementation details to the extent
possible,
all queries of Items might be against views built on the Item tables described
above.
Specifically, views may be created for each Item type against the appropriate
type family table.
These type views may select all Items of the associated type, including sub-
types. For
convenience, in addition to the UDT object, the views may expose columns for
all of the top-
level fields of that type, including inherited fields.
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3. Extension Mapping
[0209] Extensions are very similar to Items and have some of the same
requirements.
As another root type supporting inheritance, Extensions are subject to many of
the same
considerations and trade-offs in storage. Because of this, a similar type
family mapping is
applied to Extensions, rather than a single table approach. Of course, in
other embodiments, a
single table approach could be used. In the present embodiment, an Extension
is associated with
exactly one Item by ItemID, and contains an ExtensionlD that is unique in the
context of the
Item. As with Items, a function might be provided to retrieve an Extension
given its identity,
which consists of an ItemID and ExtensionlD pair. A View is created for each
Extension type,
similar to the Item type views.
4. Nested Element Mapping
[0210] Nested Elements are types that can be embedded in Items, Extensions,
Relationships, or other Nested Elements to form deeply nested structures. Like
Items and
Extensions, Nested Elements are implemented as UDT's, but they are stored
within an Items and
Extensions. Therefore, Nested Elements have no storage mapping beyond that of
their Item and
Extension containers. In other words, there are no tables in the system which
directly store
instances of NestedElement types, and there are no views dedicated
specifically to Nested
Elements.
5. Object Identity
[0211] Each entity in the data model, i.e., each Item, Extension and
Relationship, has a
unique key value. An Item is uniquely identified by its Itemld. An Extension
is uniquely
identified by a composite key of (Itemld, Extensionld). A Relationship is
identified by a
composite key (Itemld, Relationshipld). Itemld, Extensionld and Relationshipld
are GUID
values.
6. SQL Object Naming
[0212] All objects created in the data store can be stored in a SQL schema
name
derived from the storage platform schema name. For example, the storage
platform Base
schema (often called "Base") may produce types in the "[System. Storage]" SQL
schema such as
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"[System. Storage].Item". Generated names are prefixed by a qualifier to
eliminate naming
conflicts. Where appropriate, an exclamation character (!) is used as a
separator for each logical
part of the name. The table below outlines the naming convention used for
objects in the data
store. Each schema element (Item, Extension, Relationship and View), is listed
along with the
decorated naming convention used to access instances in the data store.
Object Name Decoration Description Example
Master Item Master!Item Provides a [System. Storage].
Search View summary of items [Master!Item]
in the current
item domain.
Typed Item Item Type Provides all [AcmeCorp.Doc].,
search view property data [OfficeDoc]
from item and any
parent type(s).
Master Master!Extension Provides a [System. Storage].
Extension summary of all [Master!Extension]
Search View extensions in the
current item
domain.
Typed Extension! extensionType Provides all [AcmeCorp.Doc].
extension property data for [Extension! StickyNote]
search view extension.
Master Master!Relationship Provides a [System. Storage].
Relationship summary of all [Master!Relationship]
View relationships in
the current item
domain.
Relationship Relationship! relationship Provides all data [AcmeCorp.Doc].
view Name associated with a [Relationship!AuthorsFrom
given relationship Document]
View View!viewName Provides the [AcmeCorp.Doc].
columns/types [View!DocumentTitles]
based on the
schema view
definition.
7. Column Naming
[02131 When mapping any object model into a store, the possibility of naming
collisions occur due to additional information stored along with an
application object. In order
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to avoid naming collisions, all non-type specific columns (columns which do
not map directly to
a named Property in a type declaration) is be prefixed with an underscore (J
character. In the
present embodiment, underscore U characters are disallowed as the beginning
character of any
identifier property. Further, in order to unify naming between CLR and the
data store, all
properties of a storage platform types or schema element (relationship, etc.)
should have a
capitalized first character.
8. Search Views
[0214] Views are provided by the storage platform for searching stored
content. A
SQL view is provided for each Item and Extension type. Further, views are
provided to support
Relationships and Views (as defined by the Data Model). All SQL views and
underlying tables
in the storage platform are read-only. Data may be stored or changed using the
Update()
method of the storage platform API, as described more fully below.
[0215] Each view explicitly defined in a storage platform schema (defined by
the
schema designer, and not automatically generated by the storage platform) is
accessible by the
named SQL view [<schema-name>].[View!<view-name>]. For example, a view named
"BookSales" in the schema "AcmePublisher.Books" would be accessible using the
name
"[AcmePublisher.Books].[View!BookSales]". Since the output format of a view is
custom on a
per-view basis (defined by an arbitrary query provided by the party defining
the view), the
columns are directly mapped based on the schema view definition.
[0216] All SQL search views in the storage platform data store use the
following
ordering convention for columns:
= Logical "key" column (s) of view result such as Iternld, Elementld,
Relationshipld, ...
= Metadata information on type of result such as Typeld.
= Change tracking columns such as CreateVer sion, Update Version, ...
= Type specific column(s) (Properties of the declared type)
= Type specific views (family views) also contain an object column which
returns
the object
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[0217] Members of each type family are searchable using a series of Item
views, with
there being one view per Item type in the data store. Fig. 28 is a diagram
illustrating the concept
of an Item search view.
a) Item
[0218] Each Item search view contains a row for each instance of an Item of
the
specific type or its subtypes. For example, the view for Document could return
instances of
Document, LegalDocument and ReviewDocument. Given this example, the Item views
can be
conceptualized as shown in Fig. 29.
(1) Master Item Search View
[0219] Each instance of a storage platform data store defines a special Item
view called
the Master Item View. This view provides summary information on each Item in
the data store.
The view provides one column per Item type property, a column which described
the type of the
Item and several columns which are used to provide change tracking and
synchronization
information. The master item view is identified in a data store using the name
"[System. Storage]. [Master!Item]".
Column Type Description
Itemld Itemld The storage platform identity of the Item
_TypeId Typeld The Typeld of the Item - identifies the exact type of
the Item and can be used to retrieve information on
the type using a Metadata catalog.
_Rootltemld Itemld The Itemld of the first non-embedded ancestor that
controls the lifetime of this item.
<global ... Global change tracking information
change
tracking>
<Item props> n/a One column per Item type property
(2) Typed Item Search Views
[0220] Each Item type also has a search view. While similar to the root Item
view, this
view also provides access to the Item object via the "_Item" column. Each
typed item search
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view is identified in a data store using the name [schemaName].[item
TypeName]. For example
[AcmeCorp.Doc]. [OfficeDoc].
Column Type Description
Itemld Itemld The storage platform identity of the Item
<type change ... Type change tracking information
tracking>
<parent props> <property One column per parent property
specific>
<item props> property One column per exclusive property of this type
specific>
Item CLR type of Item CLR object - type of declared Item
b) Item Extensions
[0221] All Item Extensions in a WinFS Store are also accessible using search
views.
(1) Master Extension Search View
[0222] Each instance of a data store defines a special Extension view called
the Master
Extension View. This view provides summary information on each Extension in
the data store.
The view has a column per Extension property, a column which describes the
type of the
Extension and several columns which are used to provide change tracking and
synchronization
information. The master extension view, is identified in a data store using
the name
"[System. Storage]. [Master! Extension]".
Column Type Description
ItemId Itemld The storage platform identity of the Item with which
this extension is associated
Extensionld Extensionld Id of this extension instance
(GUID)
_Typeld Typeld The TypeId of the Extension - identifies the exact
type of the extension and can be used to retrieve
information on the extension using the Metadata
catalog.
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<global change ... Global change tracking information
tracking>
<ext properties> <property One column per Extension type property
specific>
(2) Typed Extension Search Views
[0223] Each Extension type also has a search view. While similar to the master
extension view, this view also provides access to the Item object via the
Extension column.
Each typed extension search view is identified in a data store using the name
[schemaName]. [Extension! extensionTypeName]. For example
[AcmeCorp.Doc]. [Extension! OfficeDocExt].
Column Type Description
Itemld Itemld The storage platform identity of the Item with
which this extension is associated
Extensionld Extensionld Id of this extension instance
(GUID)
<type change ... Type change tracking information
tracking>
<parent <property One column per parent property
props> specific>
<ext props> property One column per exclusive property of this type
specific>
_Extension CLR type of CLR object - type of declared Extension
Extension
instance
c) Nested Elements
[0224] All nested elements are stored within Items, Extensions or
Relationships
instances. As such, they are accessed by querying the appropriate Item,
Extension, or
Relationship search view.
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d) Relationships
[0225] As discussed above, Relationships form the fundamental unit of linking
between
Items in a storage platform data store.
(1) Master Relationship Search View
[0226] Each data store provides a Master Relationship View. This view provides
information on all relationship instances in the data store. The master
relationship view is
identified in a data store using the name "[System. Storage]. [Master!
Relationship]".
Column Type Description
ItemId ItemId Identity of source endpoint (Itemld)
Relationshipld Relationshipld The id of the relationship instance
(GUID)
RelTypeId RelationshipTypeld The RelTypeld of the Relationship - identifies
the type of the relationship instance using the
Metadata catalog.
<global change ... Global change tracking information.
tracking>
TargetltemReference ItemReference Identity of target endpoint
_Relationship Relationship Instance of the Relationship object for this
instance
(2) Relationship Instance Search Views
[0227] Each declared Relationship also has a search view which returns all
instances of
the particular relationship. While similar to the master relationship view,
this view also
provides named columns for each property of the relationship data. Each
relationship instance
search view is identified in a data store using the name
[schemaName].[Relationship!relationshipName]. For example
[AcmeCorp.Doc]. [Relationship ! DocumentAuthor] .
Column Type Description
ItemId ItemId Identify of source endpoint (Itemld)
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Relationshipld Relationshipld The id of the relationship instance
(GUID)
<type change ... Type change tracking information
tracking>
TargetltemReference ItemReference Identity of target endpoint
<source name> Itemld Named property of source endpoint identity
(alias for ItemId)
<target name> ItemReference or Named property of target endpoint identity
derived class (alias and cast for TargetltemReference)
<rel property> <property One column per property of the relationship
specific> definition
_Relationship CLR type of
Relationship CLR object - type of declare Relationship
instance
e)
9. Updates
[0228] All views in the storage platform data store are read-only. In order to
create a
new instance of a data model element (item, extension or relationship), or to
update an existing
instance, the ProcessOperation or ProcessUpdategram methods of the storage
platform API must
be used. The ProcessOperation method is a single stored procedure defined by
the data store
which consumes an "operation" that details an action to be performed. The
ProcessUpdategram
method is a stored procedure which takes an ordered set of operations, known
as an
"updategram", which collectively detail a set of actions to be performed..
[0229] The operation format is extensible and provides various operations over
the
schema elements. Some common operations include:
1. Item operations:
a. Createltem (Creates a new item in the context of an embedding or holding
relationship)
b. Updateltem (updates an existing Item)
2. Relationship operations:
a. CreateRelationship (creates an instance of a reference or holding
relationship)
b. UpdateRelationship (updates a relationship instance)
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c. DeleteRelationship (removes a relationship instances)
3. Extension operations:
a. CreateExtension (adds an extension to an existing Item)
b. UpdateExtension (updates an existing extension)
c. DeleteExtension (deletes an extension)
10. Change Tracking & Tombstones
[0230] Change tracking and tombstone services are provided by the data store,
as
discussed more fully below. This section provides an outline of the change
tracking information
exposed in a data store.
a) Change Tracking
[0231] Each search view provided by the data store contains columns used to
provide
change tracking information; the columns are common across all Item, Extension
and
Relationship views. Storage platform Schema Views, defined explicitly by
schema designers,
do not automatically provide change tracking information - such information is
provided
indirectly through the search views on which the view itself is built.
[0232] For each element in the data store, change tracking information is
available from
two places - the "master" element view and the "typed" element view. For
example, change
tracking information on the AcmeCorp.Document.Document Item type is available
from the
Master Item View "[System. Storage].[Master!Item]" and typed Item search view
[AcmeCorp.Do cument] . [Document].
(1) Change Tracking in "Master" Search Views
[0233] Change tracking information in the master search views provides
information on
the creation and update versions of an element, information on which sync
partner created the
element, which sync partner last updated the element and the version numbers
from each partner
for creation and update. Partners in sync relationships (described below) are
identified by
partner key. A single UDT object named _ChangeTrackingInfo of type
[System. Storage. Store].ChangeTrackingInfo contains all this information. The
type is defined in
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the System. Storage schema. _ChangeTrackinglnfo is available in all global
search views for
Item, Extension and Relationship. The type definition of ChangeTrackinglnfo
is:
<Type Name=" ChangeTrackinglnfo" BaseType=" Base. NestedElement">
<FieldProperty Name="CreationLocalTS" Type=" SglTypes.SglInt64"
Nullable="False" />
<FieldProperty Name=" CreatingPartnerKey"
Type=" SglTypes . Sg1Int32" Nullable=" False" />
<FieldProperty Name="CreatingPartnerTS"
Type="Sg1Types.SglInt64" Nullable="False" />
<FieldProperty Name="LastUpdateLocalTS"
Type="SglTypes. Sg1Int64" Nullable="False" />
<FieldProperty Name="LastUpdatingPartnerKey"
Type="SglTypes. Sg1Int32" Nullable="False" />
<FieldProperty Name=" Las tUpdat ingPartnerTS" Type=" SglTypes.SglInt64"
Nullable="False" />
</Type>
These properties contain the following information:
Column Description
CreationLocalTS Creation time stamp by the local machine
_CreatingPartnerKey PartnerKey of the partner who created this entity.
If the entity was locally created, this is the local
machine's PartnerKey.
_CreatingPartnerTS Timestamp of the time at which this entity was
created at the partner corresponding to
CreatingPartnerKey.
_LastUpdateLocalTS Local timestamp corresponding to the update time
at the local machine
_LastUpdatingPartnerKey PartnerKey of the partner who last updated this
entity. If the last update to the entity was done
locally, this is the local machine's PartnerKey.
_LastUpdatingPartnerTS Timestamp of the time at which this entity was
updated at the partner corresponding to
_LastUpdatingPartnerKey.
(2) Change Tracking in "Typed" Search Views
[02341 In addition to providing the same information as the global search
view, each
typed search view provides additional information recording the sync state of
each element in the
sync topology.
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Column Type Description
<global change ... Information from global change
tracking> tracking
_ChangeUnitVersions MultiSet<ChangeUnitVersion> Description of version numbers
of the Change Units within the
particular element
_ElementSyncMetadata ElementSyncMetadata Additional version-independent
metadata about this item that is
only of interest to the
Synchronization runtime.
_VersionSyncMetadata VersionSyncMetadata Additional version-specific
metadata about this version that
is only of interest to the
Synchronization runtime
b) Tombstones
[0235] The data store provides tombstone information for Items, Extensions and
Relationships. The tombstone views provide information about both live and
tombstoned entities
(items, extensions and relationships) in one place. The item and extension
tombstone views do
not provide access to the corresponding object, while the relationship
tombstone view provides
access to the relationship object (the relationship object is NULL in the case
of a tombstoned
relationship).
(1) Item Tombstones
[0236] Item tombstones are retrieved from the system via the view
[System. Storage]. [Tombstone! Item].
Column Type Description
Itemld Itemld Identity of the Item
TypelD Typeld Type of the Item
<Item properties> ... Properties defined for all items
_Rootltemld Itemld Itemld of the first non-embedding item
which contains this item.
ChangeTrackinglnfo CLR instance of Change tracking information for this item
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type
ChangeTrackinglnfo
IsDeleted BIT This is a flag that is 0 for live items, and 1
for tombstoned items.
DeletionWallclock UTCDATETIME The UTC wall clock date time according to
the partner which deleted the item. It is
NULL if the Item is live.
(2) Extension Tombstones
[0237] Extension tombstones are retrieved from the system using the view
[System. Storage]. [Tombstone! Extension]. Extension change tracking
information is similar to
that provided for Items with the addition of the Extensionld property.
Column Type Description
Itemld Itemld Identity of the Item which owns the
Extension
ExtensionId Extensionld Extension Id of the Extension
TypeID ' TypeId Type of the extension
_ChangeTrackinglnfo CLR instance of Change tracking information for this
type extension
ChangeTrackinglnfo
_IsDeleted BIT This is a flag that is 0 for live items, and 1
for tombstoned extensions.
_DeletionWallclock UTCDATETIME The UTC wall clock date time according to
the partner which deleted the extension. It is
NULL if the extension is live.
(3) Relationships Tombstone
[0238] Relationship tombstones are retrieved from the system via the view
[System. Storage]. [Tombstone! Relationship]. Relationships tombstone
information is similar to
that provided for Extensions. However, additional information is provided on
the target ItemRef
of the relationship instance. In addition, the relationship object is also
selected.
Column Type Description
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Itemld Itemld Identity of the Item which owned the
relationship (identity of relationship source
endpoint)
Relationshipld Relationshipld Relationshiptd of the relationship
_TypelD Typeld Type of the relationship
_ChangeTrackinglnfo CLR instance of Change tracking information for this
type relationship
ChangeTrackinglnfo
_IsDeleted BIT This is a flag that is 0 for live items, and 1
for tombstoned extensions.
DeletionWallclock UTCDATETIME The UTC wall clock date time according to
the partner which deleted the relationship. It
is NULL if the relationship is live.
_Relationship CLR instance of a This is the relationship object for live
Relationship relationship. It is NULL for tombstoned
relationships.
TargetItemReference ItemReference Identity of target endpoint
(4) Tombstone Cleanup
[0239] In order to prevent unbounded growth of tombstone information, the data
store
provides a tombstone cleanup task. This task determines when tombstone
information may be
discarded. The task computes a bound on the local create / update version and
then truncates
the tombstone information by discarding all earlier tombstone versions.
11. Helper APIs and Functions
[0240] The Base mapping also provides a number of helper functions. These
functions
are supplied to aid common operations over the data model.
a) Function [System.Storage].Getltem
Returns an Item object given an Item Id
Item Getltem (Itemld Itemld)
b) Function [System.Storage].GetExtension
// Returns an extension object given an Itemid and Extensionld
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Extension GetExtension (Itemld Itemld, Extensionld Extensionld)
c) Function [System.Storage].GetRelationship
Returns an relationship object given an Itemld and Relationshipld
Relationship GetRelationship (Itemid Itemld, Relationshipld Relationshipld)
12. Metadata
[0241] There are two types of metadata represented in the Store: instance
metadata (the
type of an Item, etc), and type metadata.
a) Schema Metadata
[0242] Schema metadata is stored in the data store as instances of Item types
from the
Meta schema.
b) Instance Metadata
[0243] Instance metadata is used by an application to query for the type of an
Item and
finds the extensions associated with an Item. Given the Itemld for an Item, an
application can
query the global item view to return the type of the Item and use this value
to query the
Meta.Type view to return information on the declared type of the Item. For
example,
Return metadata Item object for given Item instance
//
SELECT m._Item AS metadatalnfoObj
FROM [System.Storage].[ltem] i INNER JOIN [Meta].[Type] m ON i._Typeld =
m.itemld
WHERE i.Itemld = @Itemld
E. SECURITY
[0244] In general, all securable objects arrange their access rights using the
access
mask format shown in the Fig. 26. In this format, the low-order 16 bits are
for object-specific
access rights, the next 7 bits are for standard access rights, which apply to
most types of objects,
and the 4 high-order bits are used to specify generic access rights that each
object type can map
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to a set of standard and object-specific rights. The ACCESS-SYSTEM-SECURITY
bit
corresponds to the right to access the object's SACL.
[0245] In the access mask structure of Fig. 26, item specific rights are
placed in the
Object Specific Rights section (low order 16-bits). Because in the present
embodiment, the
storage platform exposes two sets of APIs to administer security - Win32 and
the storage
platform API, the file system object specific rights must be considered in
order to motivate the
design of the storage platform object specific rights.
[0246] The security model for the storage platform of the present invention is
fully
described in the related applications incorporated by reference earlier
herein. In this regard, Fig.
27 (parts a, b, and c) depicts a new identically protected security region
being carved out of an
existing security region, in accordance with one embodiment of a security
model.
F. NOTIFICATIONS AND CHANGE TRACKING
[0247] According to another aspect of the present invention, the storage
platform
provides a notifications capability that allows applications to track data
changes. This feature is
primarily intended for applications which maintain volatile state or execute
business logic on
data change events. Applications register for notifications on items, item
extensions and item
relationships. Notifications are delivered asynchronously after data changes
have been
committed. Applications may filter notifications by item, extension and
relationship type as well
as type of operation.
[0248] According to one embodiment, the storage platform API 322 provides two
kinds
of interfaces for notifications. First, applications register for simple data
change events triggered
by changes to items, item extensions and item relationships. Second,
applications create
"watcher" objects to monitor sets of items, item extensions and relationships
between items. The
state of a watcher object can be saved and re-created after a system failure
or after a system has
gone off-line for an extended period of time. A single notification may
reflect multiple updates.
[0249] Additional details regarding this functionality can be found in the
related
applications incorporated by reference earlier herein.
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G. TRADITIONAL FILE SYSTEM INTEROPERABILITY
102501 As mentioned above, the storage platform of the present invention is,
in at least
some embodiments, intended to be embodied as an integral part of the
hardware/software
interface system of a computer system. For example, the storage platform of
the present
invention may be embodied as an integral part of an operating system, such as
the Microsoft
Windows family of operating systems. In that capacity, the storage platform
API becomes a part
of the operating system APIs through which application programs interact with
the operating
system. Thus, the storage platform becomes the means through which application
programs
store information on the operating system, and the Item based data model of
the storage platform
therefore replaces the traditional files system of such an operating system.
For example, as
embodied in the Microsoft Windows family of operating systems, the storage
platform might
replace the NTFS file system implemented in that operating system. Presently,
application
programs access the services of the NTFS file system through the Win32 APIs
exposed by the
Windows family of operating systems.
[02511 Recognizing, however, that completely replacing the NTFS file system
with the
storage platform of the present invention would require recoding of existing
Win32-based
application programs and that such recoding may be undesirable, it would be
beneficial for the
storage platform of the present invention to provide some interoperability
with existing file
systems, such as NTFS. In one embodiment of the present invention, therefore,
the storage
platform enables application programs which rely on the Win32 programming
model to access
the contents of both the data store of the storage platform as well as the
traditional NTFS file
system. To this end, the storage platform uses a naming convention that is a
superset of the
Win32 naming conventions to facilitate easy interoperability. Further, the
storage platform
supports accessing files and directories stored in a storage platform volume
through the Win32
API.
[0252] Additional details regarding this functionality can be found in the
related
applications incorporated by reference earlier herein.
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H. STORAGE PLATFORM API
[0253] The storage platform comprises an API that enables application programs
to
access the features and capabilities of the storage platform discussed above
and to access items
stored in the data store. This section describes one embodiment of a storage
platform API of the
storage platform of the present invention. Details regarding this
functionality can be found in the
related applications incorporated by reference earlier herein, with some of
this information
summarized below for convenience.
[0254] Referring to Fig. 18, a Containment Folder is an item which contains
holding
Relationships to other Items and is the equivalent of the common concept of a
file system folder.
Each Item is "contained" within at least one containment folder.
[0255] Fig. 19 illustrates the basic architecture of the storage platform API,
in
accordance with the present embodiment. The storage platform API uses
SQLClient 1900 to talk
to the local data store 302 and may also use SQLClient 1900 to talk to remote
data stores (e.g.,
data store 340). The local store 302 may also talk to the remote data store
340 using either DQP
(Distributed Query Processor) or through the the storage platform
synchronization service
("Sync") described below. The storage platform API 322 also acts as the bridge
API for data
store notifications, passing application's subscriptions to the notification
engine 332 and routing
notifications to the application (e.g., application 350a, 350b, or 350c), as
also described above.
In one embodiment, the storage platform API 322 may also define a limited
"provider"
architecture so that it can access data in Microsoft Exchange and AD.
[0256] Fig. 20 schematically represents the various components of the storage
platform
API. The storage platform API consists of the following components: (1) data
classes 2002,
which represent the storage platform element and item types, (2) runtime
framework 2004,
which manages object persistence and provides support classes 2006; and (3)
tools 2008, which
are used to generate CLR classes from the storage platform schemas.
[0257] The hierarchy of classes resulting from a given schema directly
reflects the
hierarchy of types in that schema. As an example, consider the Item types
defined in the Contacts
schema as shown in Fig. 21A and Fig. 21B.
[0258] Fig. 22 illustrates the runtime framework in operation. The runtime
framework
operates as follows:
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1. An application 350a, 350b, or 350c binds to an item in the storage
platform.
2. The framework 2004 creates an ItemContext object 2202 corresponding to the
bound
item and returns it to the application.
3. The application submits a Find on this ItemContext to get a collection of
Items; the
returned collection is conceptually an object graph 2204 (due to
relationships).
4. The application changes, deletes, and inserts data.
5. The application saves the changes by calling the Update() method.
[02591 Fig. 23 illustrates the execution of a "FindAll" operation.
[0260] Fig. 24 illustrates the process by which storage platform API classes
are
generated from the storage platform Schema
[0261] Fig. 25 illustrates the schema on which the File API is based. The
storage
platform API includes a namespace for dealing with file objects. This
namespace is called
System.Storage.Files. The data members of the classes in System.Storage.Files
directly reflect
the information stored in the storage platform store; this information is
"promoted" from the file
system objects or maybe created natively using the Win32 API. The
System.Storage.Files
namespace has two classes: FileItem and Directoryltem. The members of these
classes and
methods thereof can be readily divined by looking at the schema diagram in
Fig. 25. FileItem
and Directoryltem are read-only from the storage platform API. In order to
modify them, one has
to use the Win32 API or classes in System.IO.
[0262] In regard to APIs, a programming interface (or more simply, interface)
may be
viewed as any mechanism, process, protocol for enabling one' or more
segment(s) of code to
communicate with or access the functionality provided by one or more other
segment(s) of code.
Alternatively, a programming interface may be viewed as one or more
mechanism(s), method(s),
function call(s), module(s), object(s), etc. of a component of a system
capable of communicative
coupling to one or more mechanism(s), method(s), function call(s), module(s),
etc. of other
component(s). The term "segment of code" in the preceding sentence is intended
to include one
or more instructions or lines of code, and includes, e.g., code modules,
objects, subroutines,
functions, and so on, regardless of the terminology applied or whether the
code segments are
separately compiled, or whether the code segments are provided as source,
intermediate, or
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object code, whether the code segments are utilized in a runtime system or
process, or whether
they are located on the same or different machines or distributed across
multiple machines, or
whether the functionality represented by the segments of code are implemented
wholly in
software, wholly in hardware, or a combination of hardware and software.
[0263] Notionally, a programming interface may be viewed generically, as shown
in
Fig. 30A or Fig. 30B. Fig. 30A illustrates an interface Interface1 as a
conduit through which first
and second code segments communicate. Fig. 30B illustrates an interface as
comprising interface
objects 11 and 12 (which may or may not be part of the first and second code
segments), which
enable first and second code segments of a system to communicate via medium M.
In the view of
Fig. 30B, one may consider interface objects 11 and 12 as separate interfaces
of the same system
and one may also consider that objects 11 and 12 plus medium M comprise the
interface.
Although Figs. 30A and 30B show bi-directional flow and interfaces on each
side of the flow,
certain implementations may only have information flow in one direction (or no
information
flow as described below) or may only have an interface object on one side. By
way of example,
and not limitation, terms such as application programming interface (API),
entry point, method,
function, subroutine, remote procedure call, and component object model (COM)
interface, are
encompassed within the definition of programming interface.
[0264] Aspects of such a programming interface may include the method whereby
the
first code segment transmits information (where "information" is used in its
broadest sense and
includes data, commands, requests, etc.) to the second code segment; the
method whereby the
second code segment receives the information; and the structure, sequence,
syntax, organization,
schema, timing and content of the information. In this regard, the underlying
transport medium
itself may be unimportant to the operation of the interface, whether the
medium be wired or
wireless, or a combination of both, as long as the information is transported
in the manner
defined by the interface. In certain situations, information may not be passed
in one or both
directions in the conventional sense, as the information transfer may be
either via another
mechanism (e.g. information placed in a buffer, file, etc. separate from
information flow between
the code segments) or non-existent, as when one code segment simply accesses
functionality
performed by a second code segment. Any or all of these aspects may be
important in a given
situation, e.g., depending on whether the code segments are part of a system
in a loosely coupled
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or tightly coupled configuration, and so this list should be considered
illustrative and non-
limiting.
[0265] This notion of a programming interface is known to those skilled in the
art and
is clear from the foregoing detailed description of the invention. There are,
however, other ways
to implement a programming interface, and, unless expressly excluded, these
too are intended to
be encompassed by the claims set forth at the end of this specification. Such
other ways may
appear to be more sophisticated or complex than the simplistic view of Figs.
30A and 30B, but
they nonetheless perform a similar function to accomplish the same overall
result. We will now
briefly describe some illustrative alternative implementations of a
programming interface.
[0266] Factoring: A communication from one code segment to another may be
accomplished indirectly by breaking the communication into multiple discrete
communications.
This is depicted schematically in Figs. 3 1A and 31B. As shown, some
interfaces can be
described in terms of divisible sets of functionality. Thus, the interface
functionality of Figs.
30A and 30B may be factored to achieve the same result, just as one may
mathematically
provide 24, or 2 times 2 time 3 times 2. Accordingly, as illustrated in Fig.
31A, the function
provided by interface Interface1 may be subdivided to convert the
communications of the
interface into multiple interfaces InterfacelA, Interface 1B, Interface 1C,
etc. while achieving the
same result. As illustrated in Fig. 31B, the function provided by interface I1
may be subdivided
into multiple interfaces Ila, I1b, Ilc, etc. while achieving the same result.
Similarly, interface 12
of the second code segment which receives information from the first code
segment may be
factored into multiple interfaces 12a, 12b, 12c, etc. When factoring, the
number of interfaces
included with the lst code segment need not match the number of interfaces
included with the
2nd code segment. In either of the cases of Figs. 31A and 31B, the functional
spirit of interfaces
Interfacel and 11 remain the same as with Figs. 30A and 30B, respectively. The
factoring of
interfaces may also follow associative, commutative, and other mathematical
properties such that
the factoring may be difficult to recognize. For instance, ordering of
operations may be
unimportant, and consequently, a function carried out by an interface may be
carried out well in
advance of reaching the interface, by another piece of code or interface, or
performed by a
separate component of the system. Moreover, one of ordinary skill in the
programming arts can
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appreciate that there are a variety of ways of making different function calls
that achieve the
same result.
[0267] Redefinition: In some cases, it may be possible to ignore, add or
redefine
certain aspects (e.g., parameters) of a programming interface while still
accomplishing the
intended result. This is illustrated in Figs. 32A and 32B. For example, assume
interface
Interface1 of Fig. 30A includes a function call Square(input, precision,
output), a call that
includes three parameters, input, precision and output, and which is issued
from the 1st Code
Segment to the 2nd Code Segment. If the middle parameter precision is of no
concern in a given
scenario, as shown in Fig. 32A, it could just as well be ignored or even
replaced with a
meaningless (in this situation) parameter. One may also add an additional
parameter of no
concern. In either event, the functionality of square can be achieved, so long
as output is returned
after input is squared by the second code segment. Precision may very well be
a meaningful
parameter to some downstream or other portion of the computing system;
however, once it is
recognized that precision is not necessary for the narrow purpose of
calculating the square, it
may be replaced or ignored. For example, instead of passing a valid precision
value, a
meaningless value such as a birth date could be passed without adversely
affecting the result.
Similarly, as shown in Fig. 32B, interface I1 is replaced by interface I1',
redefined to ignore or
add parameters to the interface. Interface 12 may similarly be redefined as
interface I2', redefined
to ignore unnecessary parameters, or parameters that may be processed
elsewhere. The point
here is that in some cases a programming interface may include aspects, such
as parameters, that
are not needed for some purpose, and so they may be ignored or redefined, or
processed
elsewhere for other purposes.
[0268] Inline Coding: It may also be feasible to merge some or all of the
functionality
of two separate code modules such that the "interface" between them changes
form. For
example, the functionality of Figs. 30A and 30B maybe converted to the
functionality of Figs.
33A and 33B, respectively. In Fig. 33A, the previous 1st and 2nd Code Segments
of Fig. 30A are
merged into a module containing both of them. In this case, the code segments
may still be
communicating with each other but the interface may be adapted to a form which
is more
suitable to the single module. Thus, for example, formal Call and Return
statements may no
longer be necessary, but similar processing or response(s) pursuant to
interface Interfacel may
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still be in effect. Similarly, shown in Fig. 33B, part (or all) of interface
12 from Fig. 30B may be
written inline into interface I1 to form interface I1". As illustrated,
interface 12 is divided into 12a
and 12b, and interface portion 12a has been coded in-line with interface Il to
form interface 11
".
For a concrete example, consider that the interface I1 from Fig. 30B performs
a function call
square (input, output), which is received by interface 12, which after
processing the value passed
with input (to square it) by the second code segment, passes back the squared
result with output.
In such a case, the processing performed by the second code segment (squaring
input) can be
performed by the first code segment without a call to the interface.
[0269] Divorce: A communication from one code segment to another may be
accomplished indirectly by breaking the communication into multiple discrete
communications.
This is depicted schematically in Figs. 34A and 34B. As shown in Fig. 34A, one
or more piece(s)
of middleware (Divorce Interface(s), since they divorce functionality and / or
interface functions
from the original interface) are provided to convert the communications on the
first interface,
Interfacel, to conform them to a different interface, in this case interfaces
Interface2A,
Interface2B and Interface2C. This might be done, e.g., where there is an
installed base of
applications designed to communicate with, say, an operating system in
accordance with an
Interfacel protocol, but then the operating system is changed to use a
different interface, in this
case interfaces Interface2A, Interface2B and Interface2C. The point is that
the original interface
used by the 2nd Code Segment is changed such that it is no longer compatible
with the interface
used by the 1st Code Segment, and so an intermediary is used to make the old
and new interfaces
compatible. Similarly, as shown in Fig. 34B, a third code segment can be
introduced with
divorce interface DI1 to receive the communications from interface I1 and with
divorce interface
D12 to transmit the interface functionality to, for example, interfaces 12a
and 12b, redesigned to
work with D12, but to provide the same functional result. Similarly, DII and
D12 may work
together to translate the functionality of interfaces 11 and 12 of Fig. 30B to
a new operating
system, while providing the same or similar functional result.
102701 Rewriting: Yet another possible variant is to dynamically rewrite the
code to
replace the interface functionality with something else but which achieves the
same overall
result. For example, there may be a system in which a code segment presented
in an intermediate
language (e.g. Microsoft IL, Java ByteCode, etc.) is provided to a Just-in-
Time (JIT) compiler or
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interpreter in an execution environment (such as that provided by the Net
framework, the Java
runtime environment, or other similar runtime type environments). The JIT
compiler may be
written so as to dynamically convert the communications from the 1st Code
Segment to the 2nd
Code Segment, i.e., to conform them to a different interface as may be
required by the 2nd Code
Segment (either the original or a different 2nd Code Segment). This is
depicted in Figs. 35A and
35B. As can be seen in Fig. 35A, this approach is similar to the Divorce
scenario described
above. It might be done, e.g., where an installed base of applications are
designed to
communicate with an operating system in accordance with an Interface I
protocol, but then the
operating system is changed to use a different interface. The JIT Compiler
could be used to
conform the communications on the fly from the installed-base applications to
the new interface
of the operating system. As depicted in Fig. 35B, this approach of dynamically
rewriting the
interface(s) may be applied to dynamically factor, or otherwise alter the
interface(s) as well.
102711 It should also be noted that the above-described scenarios for
achieving the
same or similar result as an interface via alternative embodiments may also be
combined in
various ways, serially and/or in parallel, or with other intervening code.
Thus, the alternative
embodiments presented above are not mutually exclusive and may be mixed,
matched and
combined to produce the same or equivalent scenarios to the generic scenarios
presented in Figs.
30A and 30B. It is also noted that, as with most programming constructs, there
are other similar
ways of achieving the same or similar functionality of an interface which may
not be described
herein, but nonetheless are represented by the scope of the invention, i.e.,
it is noted
that it is at least partly the functionality represented by, and the
advantageous results enabled by,
an interface that underlie the value of an interface.
M. SYNCHRONIZATION-API
[0272) Several approaches to synchronization are possible in an Item-based
hardware/software interface system. Section A discloses several embodiments of
the present
invention, while Section B focuses on various embodiments of an API for
synchronization.
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A. SYNCHRONIZATION OVERVIEW
[0273] For several embodiments of the present invention, and in regard to Fig.
3, the
storage platform provides a synchronization service 330 that (i) allows
multiple instances of the
storage platform (each with its own data store 302) to synchronize parts of
their content
according to a flexible set of rules, and (ii) provides an infrastructure for
third parties to
synchronize the data store of the storage platform of the present invention
with with other data
sources that implement proprietary protocols.
[0274] Storage-platform-to-storage-platform synchronization occurs among a
group of
participating "replicas." For example, with reference to Fig. 3, it may be
desirable to provide
synchronization between the data store 302 of the storage platform 300 with
another remote data
store 338 under the control of another instance of the storage platform,
perhaps running on a
different computer system. The total membership of this group is not
necessarily known to any
given replica at any given time.
[0275] Different replicas can make the changes independently (i.e.,
concurrently). The
process of synchronization is defined as making every replica aware of the
changes made by
other replicas. This synchronization capability is inherently multi-master.
[0276] The synchronization capability of the present invention allows replicas
to:
= determine which changes another replica is aware of;
= request information about changes that this replica is not aware of,
= convey information about changes that the other replica is not aware of;
= determine when two changes are in conflict with each other;
= apply changes locally;
= convey conflict resolutions to other replicas to ensure convergence; and
= resolve the conflicts based on specified policies for conflict resolutions.
1. Storage-Platform-to-Storage-Platform Synchronization
[0277] The primary application of the synchronization service 330 of the
storage
platform of the present invention is to synchronize multiple instances of the
storage platform
(each with its own data store). The synchronization service operates at the
level of the storage
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platform schemas (rather than the underlying tables of the database engine
314). Thus, for
example, "Scopes" are used to define synchronization sets as discussed below.
[0278] The synchronization service operates on the principle of "net changes".
Rather
than recording and sending individual operations (such as with transactional
replication), the
synchronization service sends the end-result of those operations, thus often
consolidating the
results of multiple operations into a single resulting change.
[0279] The synchronization service does not in general respect transaction
boundaries.
In other words, if two changes are made to a storage platform data store in a
single transaction,
there is no guarantee that these changes are applied at all other replicas
atomically-one may
show up without the other. The exception to this principle is that if two
changes are made to the
same Item in the same transaction, then these changes are guaranteed to be
sent and applied to
other replicas atomically. Thus, Items are the consistency units of the
synchronization service.
a) Synchronization (Sync) Controlling Applications
[0280] Any application can connect to the synchronization service and initiate
a sync
operation. Such an application provides all of the parameters needed to
perform synchronization
(see sync profile below). Such applications are referred to herein as Sync
Controlling
Applications (SCAs).
[0281] When synchronizing two storage platform instances, sync is initiated on
one
side by an SCA. That SCA informs the local synchronization service to
synchronize with the
remote partner. On the other side, the synchronization service is awoken by
the messages sent
by the synchronization service from the originating machine. It responds based
on the persistent
configuration information (see mappings below) present on the destination
machine. The
synchronization service can be run on schedule or in response to events. In
these cases, the
synchronization service implementing the schedule becomes the SCA.
[0282] To enable synchronization, two steps need to be taken. First, the
schema
designer must annotate the storage platform schema with appropriate sync
semantics
(designating Change Units as described below). Second, synchronization must be
properly
configured on all of the machines having an instance of the storage platform
that is to participate
in the synchronization (as described below).
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b) Schema annotation
[0283] A fundamental concept of the synchronization service is that of a
Change Unit.
A Change Unit is a smallest piece of schema that is individually tracked by
the storage platform.
For every Change Unit, the synchronization service may be able to determine
whether it changed
or did not change since the last sync.
[0284] Designating Change Units in the schema serves several purposes. First,
it
determines how chatty the synchronization service is on the wire. When a
change is made inside
a Change Unit, the entire Change Unit is sent to the other replicas, since the
synchronization
service does not know which part of the Change Unit was changed. Second, it
determines the
granularity of conflict detection. When two concurrent changes (these terms
are defined in detail
in subsequent sections) are made to the same Change Unit, the synchronization
service raises a
conflict; on the other hand, if concurrent changes are made to different
Change Units, then no
conflict is raised and the changes are automatically merged. Third, it
strongly affects the amount
of metadata kept by the system. Much of the synchronization service metadata
is kept per-
Change Unit; thus, making Change Units smaller increases the overhead of sync.
[0285] Defining Change Units requires finding the right trade-offs. For that
reason, the
synchronization service allows schema designers to participate in the process.
[0286] In one embodiment, the synchronization service does not support Change
Units
that are larger than an element. However, it does support the ability for
schema designers to
specify smaller Change Units than an element --- namely, grouping multiple
attributes of an
element into a separate Change Unit. In that embodiment, this is accomplished
using the
following syntax:
<Type Name="Appointment" MajorVersion="1" MinorVersion="0"
ExtendsType="Base.Item" ExtendsVersion="l ">
<Field Name="MeetingStatus" Type="the storage platformTypes.uniqueidentifier
Nullable="False"/>
<Field Name="OrganizerName" Type="the storage platformTypes.nvarchar(512)"
Nuiiable="False"/>
<Field Name="OrganizerEmail" Type="the storage platformTypes.nvarchar(512)"
TypeMajorVersion="1" MultiValued="True"/>
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<ChangeUnit Name="CU_Status">
<Field Name="MeetingStatus"/>
</ChangeUnit>
<ChangeUnit Name="CU_Organizer"/>
<Field Name="OrganizerName" />
<Field Name="OrganizerEmail" />
</ChangeUnit>
</Type>
c) Sync Configuration
[0287] A group of storage platform partners that wish to keep certain parts of
their data
in sync are referred to as a sync community. While the members of the
community want to stay
in sync, they do not necessarily represent the data in exactly the same way;
in other words, sync
partners may transform the data they are synchronizing.
[0288] In a peer-to-peer scenario, it is impractical for peers to maintain
transformation
mappings for all of their partners. Instead, the synchronization service takes
the approach of
defining "Community Folders". A community folder is an abstraction that
represents a
hypothetical "shared folder" that all community members are synchronizing
with.
[0289] This notion is best illustrated by an example. If Joe wants to keep My
Documents folders of his several computers in sync, Joe defines a community
folder called, say,
JoesDocuments. Then, on every computer, Joe configures a mapping between the
hypothetical
JoesDocuments folder and the local My Documents folder. From this point on,
when Joe's
computers synchronize with each other, they talk in terms of documents in
JoesDocuments,
rather than their local items. This way, all Joe's computers understand each
other without having
to know who the others are - the Community Folder becomes the lingua franca of
the sync
community.
[0290] Configuring the synchronization service consists of three steps: (1)
defining
mappings between local folders and community folders; (2) defining sync
profiles that determine
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what gets synchronized (e.g. whom to sync with and which subsets should be
sent and which
received); and (3) defining the schedules on which different sync profiles
should run, or running
them manually.
(1) Community Folder - Mappings
[02911 Community Folder mappings are stored as XML configuration files on
individual machines. Each mapping has the following schema:
/mappings/communityFolder
This element names the community folder that this mapping is for. The name
follows the
syntax rules of Folders.
/mappings/loealFolder
This element names the local folder that the mapping transforms into. The name
follows
the syntax rules of Folders. The folder must already exist for the mapping to
be valid.
The items within this folder are considered for synchronization per this
mapping.
/mappings/transformations
This element defines how to transform items from the community folder to the
local
folder and back. If absent or empty, no transformations are performed. In
particular, this
means that no IDs are mapped. This configuration is primarily useful for
creating a cache
of a Folder.
/mappings/transformations/mapIDs
This element requests that newly generated local IDs be assigned to all of the
items
mapped from the community folder, rather than reusing community IDs. The Sync
Runtime will maintain ID mappings to convert items back and forth.
/mappings/transformations/localRoot
This element requests that all root items in the community folder be made
children of the
specified root.
/mappings/runAs
This element controls under whose authority requests against this mapping are
processed.
If absent, sender is assumed.
/mappings/runAs/sender
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The presence of this element indicates that the sender of messages to this
mapping must
be impersonated, and requests processed under his credentials.
(2) Profiles
[0292] A Sync Profile is a total set of parameters needed to kick off
synchronization. It
is supplied by an SCA to the Sync Runtime to initiate sync. Sync profiles for
storage platform-
to-storage platform synchronization contain the following information:
= Local Folder, to serve as the source and destination for changes;
= Remote Folder name to synchronize with - this Folder must be published from
the
remote partner by way of a mapping as defined above;
= Direction - the synchronization service supports send-only, receive-only,
and
send-receive sync;
= Local Filter -- selects what local information to send to the remote
partner.
Expressed as a the storage platform query over the local folder;
= Remote Filter - selects what remote information to retrieve from the remote
partner - expressed as a storage platform query over the community folder;
= Transformations --- defines how to transform items to and from the local
format;
= Local security --- specifies whether the changes retrieved from the remote
endpoint are to be applied under the permissions of the remote endpoint
(impersonated) or the user initiating the sync locally; and
= Conflict resolution policy --- specifies whether conflicts should be
rejected,
logged, or automatically resolved - in the latter case, it specifies which
conflict
resolver to use, as well as the configuration parameters for it.
[0293] The synchronization service provides a runtime CLR class that allows
simple
building of Sync Profiles. Profiles can also be serialized to and from XML
files for easy storage
(often alongside schedules). However, there is no standard place in the
storage platform where
all the profiles are stored; SCAs are welcome to construct a profile on the
spot without ever
persisting it. Note that there is no need to have a local mapping to initiate
sync. All sync
information can be specified in the profile. The mapping is, however, required
in order to
respond to sync requests initiated by the remote side.
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(3) Schedules
[0294) In one embodiment, the synchronization service does not provide its own
scheduling infrastructure. Instead, it relies on another component to peform
this task - the
TM
Windows Scheduler available with the Microsoft Windows operating system. The
synchronization service includes a command-line utility that acts as an SCA
and triggers
synchronization based on a sync profile saved in an XML, file. This utility
makes it very easy to
configure the Windows Scheduler to run synchronization either on schedule, or
in response to
events such as user logon or logoff.
d) Conflict Handling
[0295) Conflict handling in the synchronization service is divided into three
stages: (1)
conflict detection, which occurs at change application time - this step
determines if a change can
be safely applied; (2) automatic conflict resolution and logging - during this
step (that takes place
immediately after the conflict is detected) automatic conflict resolvers are
consulted to see if the
conflict can be resolved - if not, the conflict can be optionally logged; and
(3) conflict inspection
and resolution - this step takes place if some conflicts have been logged, and
occurs outside of
the context of the sync session - at this time, logged conflicts can be
resolved and removed from
the log.
(1) Conflict Detection
[0296) In the present embodiment, the synchronization service detects two
types of
conflicts: knowledge-based and constraint-based.
(a) Knowledge- Based Conflicts
[0297) A knowledge-based conflict occurs when two replicas make independent
changes to the same Change Unit. Two changes are called independent if they
are made without
knowledge of each other -- in other words, the version of the first is not
covered by the
knowledge of the second and vice versa. The synchronization service
automatically detects all
such conflicts based on the replicas' knowledge as described above.
[02981 it is sometimes helpful to think of conflicts as forks in the version
history of a
Change Unit. If no conflicts occur in the life of a Change Unit, its version
history is a simple
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chain --- each change occurring after the previous one. In the case of a
knowledge-based
conflict, two changes occur in parallel, causing the chain to split and become
a version tree.
(b) Constraint-Based Conflicts
[0299] There are cases where independent changes violate an integrity
constraint when
applied together. For instance, two replicas creating a file with the same
name in the same
directory could cause such a conflict to occur.
[0300] A constraint-based conflict involves two independent changes (just like
a
knowledge-based one), but they do not affect the same Change Unit. Rather,
they affect
different Change Units but with a constraint existing between them.
[0301] The synchronization service detects constraint violations at change
application
time and raises constraint-based conflicts automatically. Resolving constraint-
based conflicts
usually requires custom code that modifies the changes in such as way as to
not violate the
constraint; The synchronization service does not provide a general-purpose
mechanism for doing
so.
(2) Conflict Processing
[0302] When a conflict is detected, the synchronization service can take one
of three
actions (selected by the sync initiator in the Sync Profile): (1) reject the
change, returning it back
to sender; (2) log a conflict into a conflict log; or (3) resolve the conflict
automatically.
[0303] If the change is rejected, the synchronization service acts as if the
change did
not arrive at the replica. A negative acknowledgement is sent back to the
originator. This
resolution policy is primarily useful on head-less replicas (such as file
servers) where logging
conflicts is not feasible. Instead, such replicas force the others to deal
with the conflicts by
rejecting them.
[0304] Sync initiators configure conflict resolution in their Sync Profiles.
The
synchronization service supports combining multiple conflict resolvers in a
single profile in the
following ways - first, by specifying a list of conflict resolvers to be tried
one after another, until
one of them succeeds; and second, by associating conflict resolvers with
conflict types, e.g.
directing update-update knowledge-based conflicts to one resolver, but all the
other conflicts to
the log.
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(a) Automatic Conflict Resolution
[0305] The synchronization service provides a number of default conflict
resolvers.
This list includes:
= local-wins: disregard incoming changes if in conflict with locally stored
data;
= remote-wins: disregard local data if in conflict with incoming changes;
= last-writer-wins: pick either local-wins or remote-wins per Change Unit
based on
the timestamp of the change (note that the synchronization service in general
does
not rely on clock values; this conflict resolver is the sole exception to that
rule);
= Deterministic: pick a winner in a manner that is guaranteed to be the same
on all
replicas, but not otherwise meaningful - one embodiment of the synchronization
services uses lexicographic comparisons of partner IDs to implement this
feature.
[0306] In addition, ISVs can implement and install their own conflict
resolvers.
Custom conflict resolvers may accept configuration parameters; such parameters
must be
specified by the SCA in the Conflict Resolution section of the Sync Profile.
[0307] When a conflict resolver handles a conflict, it returns the list of
operations that
need to be performed (in lieu of the conflicting change) back to the runtime.
The
synchronization service then applies these operations, having properly
adjusted remote
knowledge to include what the conflict handler has considered.
[0308] It is possible that another conflict is detected while applying the
resolution. In
such a case, the new conflict must be resolved before the original processing
resumes.
[0309] When thinking of conflicts as branches in the version history of an
item, conflict
resolutions can be viewed as joins --- combining two branches to form a single
point. Thus,
conflict resolutions turn version histories into DAGs.
(b) Conflict Logging
[0310] A very particular kind of a conflict resolver is the Conflict Logger.
The
synchronization service logs conflicts as Items of type ConflictRecord. These
records are related
back to the items that are in conflict (unless the items themselves have been
deleted). Each
conflict record contains: the incoming change that caused the conflict; the
type of the conflict:
update-update, update-delete, delete-update, insert-insert, or constraint; and
the version of the
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incoming change and the knowledge of the replica sending it. Logged conflicts
are available for
inspection and resolution as described below.
(c) Conflict Inspection and Resolution
[0311] The synchronization service provides an API for applications to examine
the
conflict log and to suggest resolutions of the conflicts in it. The API allows
application to
enumerate all conflicts, or conflicts related to a given Item. It also allows
such applications to
resolve logged conflicts in one of three ways: (1) remote wins --- accepting
the logged change
and overwriting the conflicting local change; (2) local wins --- ignoring
conflicting parts of the
logged change; and (3) suggest new change --- where the application proposes a
merge that, in
its opinion, resolves the conflict. Once conflicts are resolved by an
application, the
synchronization service removes them from the log.
(d) Convergence of Replicas and Propagation
of Conflict Resolutions
[0312] In complex synchronization scenarios, the same conflict can be detected
at
multiple replicas. If this occurs, several things can happen: (1) the conflict
can be resolved on
one replica, and the resolution be sent to the other; (2) the conflict is
resolved on both replicas
automatically; or (3) the conflict is resolved on both replicas manually
(through the conflict
inspection API).
[0313] To ensure convergence, the synchronization service forwards conflict
resolutions to other replicas. When a change that resolves a conflict arrives
at a replica, the
synchronization service automatically finds any conflict records in the log
that are resolved by
this update and eliminates them. In this sense, a conflict resolution at one
replica is binding on
all the other replicas.
[0314] If different winners are chosen by different replicas for the same
conflict, the
synchronization service applies the principle of binding conflict resolution
and picks one of the
two resolutions to win over the other automatically. The winner is picked in a
deterministic
fashion that is guaranteed to produce the same results at all times (one
embodiment uses replica
ID lexicographic comparisons).
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[0315] If different "new changes" are suggested by different replicas for the
same
conflict, the synchronization service treats this new conflict as a special
conflict and uses the
Conflict Logger to prevent it from propagating to other replicas. Such
situation commonly arises
with manual conflict resolution.
2. Synchronizing to Non-Storage Platform Data Stores
[0316] According to another aspect of the storage platform of the present
invention, the
storage platform provides an architecture for ISVs to implement Sync Adapters
that allow the
storage platform to synchronize to legacy systems such as Microsoft Exchange,
AD, Hotmail,
etc. Sync Adapters benefit from the many Sync Service provided by the
synchronization service,
as described below.
[0317] Despite the name, Sync Adapters do not need to be implemented as plug-
ins into
some storage platform architecture. If desired, a "sync adapter" can simply be
any application
that utilizes the synchronization service runtime interfaces to obtain
services such as change
enumeration and application.
[0318] In order to make it simpler for others to configure and run
synchronization to a
given backend, Sync Adapter writers are encouraged to expose the standard Sync
Adapter
interface, which runs sync given the Sync Profile as described above. The
profile provides
configuration information to the adapter, some of which adapters pass to the
Sync Runtime to
control runtime services (e.g. the Folder to synchronize).
a) Sync Services
[0319] The synchronization service provides a number of sync services to
adapter
writers. For the rest of this section, it is convenient to refer to the
machine on which the storage
platform is doing synchronization as the "client" and the non-storage platform
backend that the
adapter is talking to as the "server".
(1) Change Enumeration
[0320] Based on the change-tracking data maintained by the synchronization
service,
Change Enumeration allows sync adapters to easily enumerate the changes that
have occurred to
a data store Folder since the last time synchronization with this partner was
attempted.
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[0321] Changes are enumerated based on the concept of an "anchor" --- an
opaque
structure that represents information about the last synchronization. The
anchor takes the form
of the storage platform Knowledge, as described in the proceeding sections.
Sync adapters
utilizing change enumeration services fall into two broad categories: those
using "stored
anchors" vs. those using "supplied anchors".
[0322] The distinction is based on where the information about the last sync
is stored --
- on the client, or on the server. It is often easier for adapters to store
this information on the
client --- the backend is often not capable of conveniently storing this
information. On the other
hand, if multiple clients synchronize to the same backend, storing this
information on the client
is inefficient and in some cases incorrect --- it makes one client unaware of
the changes that the
other client has already pushed up to the server. If an adapter wants to use a
server-stored
anchor, the adapter needs to supply it back to the storage platform at the
time of change
enumeration.
[0323] In order for the storage platform to maintain the anchor (either for
local or
remote storage), the storage platform needs to be made aware of the changes
that were
successfully applied at the server. These and only these changes can be
included in the anchor.
During change enumeration, Sync Adapters use an Acknowledgement interface to
report which
changes were successfully applied. At the end of synchronization, adapters
using supplied
anchors must read the new anchor (which incorporates all of the successfully-
applied changes)
and send it to their backend.
[0324] Often, Adapters need to store adapter-specific data along with the
items they
insert into the storage platform data store. Common examples of such data are
remote IDs and
remote versions (timestamps). The synchronization service provides a mechanism
for storing
this data, and Change Enumeration provides a mechanism to receive this extra
data along with
the changes being returned. This eliminates the need for adapters to re-query
the database in
most cases.
(2) Change Application
[0325] Change Application allows Sync Adapters to apply changes received from
their
backend to the local storage platform. Adapters are expected to transform the
changes to the
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storage platform schema. Fig. 24 illustrates the process by which storage
platform API classes
are generated from the storage platform Schema.
[0326] The primary function of change application is to automatically detect
conflicts.
As in the case of Storage Platform-to-Storage Platform sync, a conflict is
defined as two
overlapping changes being made without knowledge of each other. When adapters
use Change
Application, they must specify the anchor with respect to which conflict
detection is performed.
Change Application raises a conflict if an overlapping local change that is
not covered by the
adapter's knowledge is detected. Similar to Change Enumeration, adapters may
use either stored
or supplied anchors. Change Application supports efficient storage of adapter-
specific metadata.
Such data may be attached by the adapter to the changes being applied, and
might be stored by
the synchronization service. The data might be returned on next change
enumeration.
,(3) Conflict Resolution
[0327] The Conflict Resolution mechanisms described above (logging and
automatic
resolution options) are available to sync adapters as well. Sync adapters may
specify the policy
for conflict resolution when applying changes. If specified, conflicts may be
passed on to the
specified conflict handler and resolved (if possible). Conflicts can also be
logged. It is possible
that the adapter may detect a conflict when attempting to apply a local change
to the backend. In
such a case, the adapter may still pass the conflict on to the Sync Runtime to
be resolved
according to policy. In addition, Sync Adapters may request that any conflicts
detected by the
synchronization service be sent back to them for processing. This is
particularly convenient in
the case where the backend is capable of storing or resolving conflicts.
b) Adapter Implementation
[0328] While some "adapters" are simply applications utilizing runtime
interfaces,
adapters are encouraged to implement the standard adapter interfaces. These
interfaces allow
Sync Controlling Applications to: request that the adapter perform
synchronization according to
a given Sync Profile; cancel on-going synchronization; and receive progress
reporting
(percentage complete) on an ongoing sync.
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3. Security
[0329] The synchronization service strives to introduce as little as possible
into the
security model implemented by the storage platform. Rather than defining new
rights for
synchronization, existing rights are used. Specifically,
= anyone who can read a data store Item can enumerate changes to that item;
= anyone who can write to a data store Item can apply changes to that item;
and
= anyone who can extend a data store Item can associate sync metadata with
that
item.
[03301 The synchronization service does not maintain secure authorship
information.
When a change is made at replica A by user U and forwarded to replica B, the
fact that the
change was originally made at A (or by U) is lost. If B forwards this change
to replica C, this is
done under B's authority, not that of A. This leads to the following
limitation: if a replica is not
trusted to make its own changes to an item, it cannot forward changes made by
others.
[03311 When the synchronization service is initiated, it is done by a Sync
Controlling
Application. The synchronization service impersonates the identity of the SCA
and performs all
operations (both locally and remotely) under that identity. To illustrate,
observe that user U
cannot cause the local synchronization service to retrieve changes from a
remote storage
platform for items that user U does not have read access.
4. Manageability
[03321 Monitoring a distributed community of replicas is a complex problem.
The
synchronization service may use a "sweep" algorithm to collect and distribute
information about
the status of the replicas. The properties of the sweep algorithm ensure that
information about all
configured replicas is eventually collected and that failing (non-responsive)
replicas are detected.
[0333] This community-wide monitoring information is made available at every
replica. Monitoring tools can be run at an arbitrarily-chosen replica to
examine this monitoring
information and make administrative decisions. Any configuration changes must
be made
directly at the affected replicas.
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B. SYNCHRONIZATION API OVERVIEW
(0334] In an increasingly distributed, digital world, individuals and
workgroups often
store information and data in a variety of different devices and locations.
This has fueled the
development of data synchronization services that can keep the information in
these separate,
often disparate, data stores synchronized at all times, with minimal user
intervention.
[0335] The synchronization platform of the present invention, which is part of
the rich
storage platform described in Section II herein (a.k.a., "WinFS"), addresses
three main
objectives:
= Allow applications and services to efficiently synchronize data between
different
"WinFS" stores.
= Enable developers to build rich solutions for synchronizing data between
"WinFS" and non-"WinFS" stores.
= Provide developers with appropriate interfaces to customize the
synchronization
user experience.
1. General Terminology
[0336] Herein below are some further refined definitions and key concepts
relevant to
later discussions herein this Section III.B:
[0337] Sync Replica: Most applications are only interested in tracking,
enumerating and
synchronizing changes for a given subset of items within the WinFS store. The
set of items that
take part in a synchronization operation is termed as a Synchronization
Replica. A Replica is
defined in terms of items contained within a given WinFS containment hierarchy
(usually rooted
at a Folder item). All synchronization services are carried out within the
context of a given
replica. WinFS Sync provides a mechanism to define, manage and cleanup
replicas. Every
replica has a GUID identifier that uniquely identifies it within a given WinFS
store.
[0338] Sync Partner: A sync partner is defined as an entity capable of
affecting changes
on WinFS items, extensions and relationships. Thus, every WinFS store can be
termed as a sync
partner. When synchronizing with a non-WinFS store, the external data source
(EDS) is also
termed as a sync partner. Every partner has a GUID identifier that uniquely
identifies it.
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10339] Sync Community: A synchronization community is defined as a collection
of
replicas that are kept in sync by means of peer-to-peer synchronization
operations. These replicas
may all be in the same WinFS store, different WinFS stores, or even manifest
themselves as
virtual replicas on non-WinFS stores. WinFS sync does not prescribe or mandate
any specific
topology for the community, especially if the only sync operations in the
community are through
the WinFS Sync service (WinFS adapter). Synchronization adapters (defined
below) may
introduce their own topology restrictions.
[0340] Change Tracking, Change Units and Versions: Every WinFS store tracks
changes to all local WinFS Items, Extensions and Relationships. Changes are
tracked at the level
of change unit granularity defined in the schema. The top-level fields of any
Item, Extension and
Relationship type can be sub-divided by the schema designer into change units,
with the smallest
granularity being one top-level field. For change tracking purposes, every
change unit is assigned
a Version, where a version is a pair of sync partner id and a version number
(the version number
is a partner-specific monotonically increasing number). Versions are updated
as changes happen
in the store locally or as they are obtained from other replicas.
[0341] Sync Knowledge: Knowledge represents the state of a given sync replica
at any
time, i.e. it encapsulates meta-data about all the changes a given replica is
aware of, either local
or from other replicas. WinFS sync maintains and updates knowledge for sync
replicas across
sync operations. Important thing to note is that the Knowledge representation
allows it to be
interpreted with respect to the entire community and not just relative to the
particular replica
where the Knowledge is stored.
[0342] Sync Adapters: A synchronization adapter is a managed code application
that
accesses WinFS Sync services through the Sync Runtime API and enables
synchronization of
WinFS data to a non-WinFS data store. Depending on the requirements of the
scenario, it's upto
the adapter developer as to which subset of WinFS data and what WinFS data
types to
synchronize. The adapter is responsible for communication with the EDS,
transforming WinFS
schemas to and from EDS supported schemas and defining and managing its own
configuration
and metadata. Adapters are strongly encouraged to implement the WinFS Sync
Adapter API to
take advantage of the common configuration and control infrastructure for
adapters provided by
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the WinFS Sync team. For more details, please refer to the WinFS Sync Adapter
API spec
[SADP] and the WinFS Sync Controller API [SCTRL] spec.
[0343] For adapters that synchronize WinFS data to external non-WinFS stores
and
cannot produce or maintain knowledge in WinFS format, WinFS Sync provides
services to
obtain remote knowledge that can be used for subsequent change enumeration or
application
operations. Depending on the capabilities of the backend store, the adapter
may wish to store this
remote knowledge on the backend or on the local WinFS store.
[0344] For simplicity, a synchronization "replica" is a structure that
represents a set of
data in a "WinFS" store that exists in a single logical location, whereas data
on a non-"WinFS"
store is called a "data source" and generally requires the use of a adapter.
[0345] Remote Knowledge: When a given sync replica wishes to obtain changes
from
another replica it provides it's own knowledge as a baseline against which the
other replica
enumerates changes. Similarly, when a given replica wishes to send changes to
another replica, it
provides it's own knowledge as a baseline which can be used by the remote
replica for detecting
conflicts. This knowledge about the other replica that's provided during sync
change
enumeration and application is termed a Remote Knowledge.
2. Synchronization API Principals
[0346] For certain embodiments, the synchronization API separates into two
parts: the
synchronization configuration API and the synchronization controller API. The
synchronization
Configuration API enables applications to configure synchronization and to
specify parameters
for a particular synchronization session between two replicas. For a given
synchronization
session, configuration parameters include the set of Items to be synchronized,
the type of
synchronization (one-way or two-way), information about the remote data
source, and the
conflict resolution policy. The synchronization controller API initiates a
synchronization
session, cancels synchronization, and receives progress and error information
about the on-going
synchronization. Moreover, for specific embodiments where synchronization
needs to be
performed on a pre-determined schedule, such systems may include scheduling
mechanism to
customize scheduling.
[0347] Several embodiments of the present invention employ synchronization
adapters
for synchronizing information between "WinFS" and non-"WinFS" data sources.
Examples of
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adapters include an adapter that synchronizes address book information between
a "WinFS"
contacts folder and a non-WinFS mailbox. In these instances, adapter
developers might use the
"WinFS" synchronization core services API described herein for accessing
services provided by
the "WinFS" synchronization platform in order to develop schema transformation
code between
the "WinFS" schema and the non-"WinFS" data source schema. Additionally, the
adapter
developer provides protocol support for communicating changes with the non-
"WinFS" data
source. A synchronization adapter is invoked and controlled by using the
synchronization
controller API and reports progress and errors using this API.
[0348] However, for certain embodiments of the present invention, when
synchronizing
"WinFS" data store with another "WinFS" data store, a synchronization adapter
may be
unnecessary if "WinFS" to "WinFS" synchronization services are integrated
within the
hardware/software interface system. In any event, several such embodiments
provides a set of
synchronization services for both "WinFS" to "WinFS" and synchronization
adapter solutions
that include:
= Tracking of changes to "WinFS" items, extensions and relationships.
= Support for efficient incremental change enumeration since a given past
state.
= Application of external changes to "WinFS".
= Conflict handling during change application.
[0349] Referring to Fig. 36, which illustrates a three instances of a common
data store
and the components for synchronizing them. A first system 3602 has a WinFS
data store 3612
comprising a WinFS-to-WinFS Sync services 3622 and Core Sync Services 3624,
for WinFS-to-
nonWinFS synchronization, which exposes 3646 a Sync API 3652 for utilization.
Similar to the
first system 3602, a second system 3604 has a WinFS data store 3614 comprising
a WinFS-to-
WinFS Sync services 3632 and Core Sync Services 3634, for WinFS-to-nonWinFS
synchronization, which exposes 3646 a Sync API 3652 for utilization. The first
system 3602 and
the second system 3604 synchronize 3642 via their respective WinFS-to-WinFS
Sync services
3622 and 3632. A third system 3606, which is not a WinFS system, has an
application for using
WinFS Sync 3666 to maintain a data source in a sync community with WinFS
replicas. This
application can utilize either a WinFS Sync Config/Control service 3664 to
directly interface
3644with the WinFS data store 3612 via the WinFS to WinFS synch services 3622
(if it is so
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capable of virtualizing itself as a WinFS data store) or via a Sync Adapter
3662 that interfaces
3648 with the Sync API 3652.
[0350] As illustrated in this figure, the first system 3602 is aware of and
directly
synchronizes with both the second system 3604 and third system 3606. However,
neither the
second system 3604 nor the third system 3606 are aware of each other and,
thus, do not
synchronize their changes directly with each other but, instead, changes that
occur on one system
must propogate through the first system 3602.
C. SYNCHRONIZATION API SERVICES
[0351] Several embodiments of the present invention are directed to
synchronization
services comprising two foundational services: change enumeration and change
application.
1. Change Enumeration
[0352] As previously discussed earlier herein, Change Enumeration allows sync
adapters to easily enumerate the changes that have occurred to a data store
Folder since the last
time synchronization with this partner was attempted based on the change-
tracking data
maintained by the synchronization service. In regard to change enumeration,
several
embodiments of the present invention are directed to:
= the efficient enumeration of changes to Items, Extensions and Relationships
in a
given replica, relative to a specified Knowledge instance.
= the enumeration of changes at the level of change unit granularity specified
in the
WinFS schemas.
= the grouping of enumerated changes in terms of compound items. A compound
item consists of an item, all its extensions, all holding relationships to the
item
and all the compound items corresponding to its embedded items. Changes to
reference relationships between items are enumearted separately.
= the batching on change enumeration. The granularity of the batch is compound
item or a relationship change (for reference relationships).
= the specification of filters over items in the replica during change
enumeration,
e.g, the replica consists of all items in a given folder, but for this
particular change
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enumeration the application would like to only enumerate changes to all
Contact
items where first name begins with an `A' (this support will be added post B-
milestone). .
= the use of remote knowledge for enumerated changes, with the ability to
record
individual change units (or entire items, extensions, or relationships) as
failed-to-
sync in the knowledge, so as to have them re-enumerated the next time around.
= the use of advanced adapters that may be capable of understanding WinFS Sync
metadata by returning metadata along with changes during change enumeration.
2. Change Application
[0353] As discussed earlier herein, change application allows Sync Adapters to
apply
changes received from their backend to the local storage platform since the
adapters are expected
to transform the changes to the storage platform schema. In regard to change
application, several
embodiments of the present invention are directed to:
= the application of incremental changes from other replicas (or non-WinFS
stores)
with corresponding updates to WinFS change metadata.
= the detection of conflicts on change application at change unit granularity.
= the reporting of success, failure and conflicts at individual change unit
level on
change application, so that applications (including adapters and sync
controlling
apps) can use that information for progress, error and status reporting and
for
updating their backend state, if any.
= the updating of remote knowledge during change application so as to prevent
"reflection" of application supplied changes during the next change
enumeration
operation.
= the use of advanced adapters that are capable of understanding and providing
WinFS Sync metadata along with changes.
3. Sample Code
[0354] The following is a code sample for how a FOO Sync adapter might
interact with
Sync Runtime (where all adapter specific functions are prefixed with FOO):
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ItemContext ctx = new ItemContext ( "\.\System\UserData\dshah\My Contacts",
true );
// Get the replica item id and remote partner id from the profile.
// Most adapters would get this information from the sync profile
Guid replicaItemId = FOO GetReplicaldQ;
Guid remotePartnerld = FOO_Get RemotePartnerld();
/1
/1 Lookup stored knowledge in the store using storedKnowledgeld like above.
//
ReplicaKnowledge remoteKnowledge = ...;
//
// Initialize ReplicaSynchronizer
//
ctx.ReplicaSynchronizer = new ReplicaSynchronizer( replicaltemld,
remotePartnerld );
ctx.ReplicaSynchronizer.RemoteKnowledge = remoteKnowledge;
ChangeReader reader = ctx.ReplicaSynchronizer.GetChangeReader();
1/ Enumerate changes and process them
//
bool bChangesToRead = true;
while (bChangesToRead)
{
ChangeCollection<object> changes = null;
bChangesToRead = reader.ReadChanges( 10, out changes );
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foreach (object change in changes)
{
// Process enumerated object, adapter does it's own schema transform
/1 and ID mapping. It may even retrieve additional objects from the
// Ctx for this purpose and modify adapter metadata after change
// has been applied to remote store
ChangeStatus status = FOOProcessAndApplyToRemoteStore(change);
// Update learned knowledge with status
reader.AcknowledgeChange ( changeStatus );
}
}
remoteKnowledge = ctx.ReplicaSynchronizer.GetUpdatedRemoteKnowledgeO;
reader.CloseQ;
11
// Save updated knowledge and adapter metadata, if any
I/
ctx.Updateo ;
//
// Sample for change application, first initialize remote knowledge using
// storedKnowledgeId as before.
//
remoteKnowledge = ...;
ctx.ReplicaSynchronizer.ConflictPolicy = conflictPolicy;
ctx.ReplicaSynchronizer.RemotePartnerld = remotePartnerld;
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ctx.ReplicaSynchronizer.RemoteKnowledge = remoteKnowledge;
ctx.ReplicaSynchronizer.ChangeStatusEvent += FOO_OnChangeStatusEvent;
//
// Obtain changes from remote store. Adapter is responsible for retrieving
// it's backend specific metadata from the store. This can be an extension
l/ on the replica.
I/
object remoteAnchor = FOO GetRemoteAnchorFromStore();
FOO RemoteChangeCollection remoteChanges = FOO_GetRemoteChanges(
remoteAnchor );
//
/I Fill in the change collection
/I
foreach( FOO RemoteChange change in remoteChanges )
{
Adapter responsible for doing ID mapping
Guid localld = FOO MapRemoteld ( change );
I/ Let's say we're syncing Person objects
ItemSearcher searcher = Person.GetSearcher( ctx );
searcher.Filters.Add( "Personld=@localld" );
searcher.Parameters["Personld"] = localld;
Person person = searcher.FindOneO;
//
// Adapter transforms remote changes to modifications on Person object
I/ As part of this adapter may even make changes to item-level backend-
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// specific metadata for the remote object.
//
FOO_TransformRemoteToLocal (remoteChange, person);
}
ctx.Update();
I/ Save the new remote anchor (this can be an extension on the replica)
FOO SaveRemoteAnchor();
//
// This is a regular WinFS API save since remote knowledge is not synced.
//
remoteKnowledge = ctx.ReplicaSynchronizer.GetUpdatedRemoteKnowledgeO;
ctx.UpdateO;
ctx.Close(;
//
/I Adapter callback for processing application status callbacks
//
void FOO OnEntitySaved( object sender, ChangeStatusEventArgs args )
{
remoteAnchor.AcceptChange( args.ChangeStatus );
}
4. Methods of API Synchronization
[0355] In one embodiment of the present invention, synchronization between a
WinFS
store and a non-WinFS store is accomplished is possible via the
Synchronization APIs exposed
by the WinFS-based hardware/software interface system.
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[0356] In one embodiment, all synchronization adapters are required to
implement the
synchronization adapter API, a common language runtime (CLR) managed API, so
that they can
be consistently deployed, initialized, and controlled. The adapter API
provides:
= A standard mechanism to register adapters with the hardware/software
interface
system synchronization framework.
= A standard mechanism for adapters to declare their capabilities and the type
of
configuration information needed to initialize the adapter.
= A standard mechanism for passing initialization information to the adapter.
= A mechanism for adapters to report progress status back to the applications
invoking
synchronization.
= A mechanism to report any errors that occur during synchronization.
= A mechanism to request cancellation of an ongoing synchronization operation.
[0357] There are two potential process models for adapters, depending on the
requirements of the scenario. The adapter can execute in the same process
space as the
application invoking it or in a separate process all by itself. To execute in
its own separate
process, the adapter defines its own factory class, which is used to
instantiate the adapter. The
factory can return an instance of the adapter in the same process as the
invoking application, or
return a remote instance of the adapter in a different Microsoft common
language runtime
application domain or process. A default factory implementation is provided
which instantiates
the adapter in the same process. In practice, many adapters will run in the
same process as the
invoking application. The out of process model is usually required for one or
both of the
following reasons:
= Security purposes. The adapter must run in the process space of a certain
process or
service.
= The adapter has to process requests from other sources - for example,
incoming
network requests - in addition to processing requests from invoking
applications.
[0358] Referring to Fig. 37, one embodiment of the present invention presumes
a
simple adapter that is unaware of how state is calculated or it associated
metadata is exchanged.
In this embodiment, synchronization is achieved by the replica, in regard to
the data source with
which it wants to synchronize, by first, at step 3702, determining which
changes have occurred
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since it last synchronized with said data source, and the replica then
transmits the incremental
changes that have occurred since this last synchronization based on its
present state information,
and this present state information and incremental changes are to the data
source via the adapter.
At step 3704, the adapter, upon receiving the change data from the replica in
the previous step,
implements as many changes to the data source as possible, tracks which
changes are successful
and which fail, and transmits the success-and-failure info back to WinFS (of
the replica). The
hardware/software interface system of the replica (WinFS), at step 3706, upon
receiving the
success-and-failure info from the replica, then calculates the new state
information for the data
source, stores this information for future use by its replica, and transmits
this new state info back
to the data source, that is, to the adapter for storage and subsequent use by
the adapter.
D. ADDITIONAL ASPECTS OF THE SYNC SCHEMA
[0359] The following are additional (or more specific) aspects of the
synchronization
schema for various embodiments of the present invention.
= Each replica is a defined synchronization subset of data from the entirety
of a data
store-a slice of data having multiple instances.
= Conflict resolution policies are handled by each replica (and adaptor/data
source
combination) individually-that is, each replica is able to resolve conflicts
based
on its own criteria and conflict resolution schema. Moreove, while differences
in
each instance of the data store may result and lead to additional future
conflicts,
the incremental and sequential enumeration of conflicts as reflected in
updated
state information is invisible to other replicas that receive that updated
state
information.
= At the root of the sync schema is the replica which has a base type to
define a root
folder (in fact, a root Item) that has a unique ID, an ID for the sync
community in
which it is a member, and whatever filters and other elements are necessary or
desireable for the specific replica.
= Each replica's "mapping" is maintained within the replica and, as such, the
mapping for any particular replica is limited to the other replicas such
replica
knows about. While this mapping may only comprise a subset of the entire sync
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community, changes to said replica will still propogate to the entire sync
community via commonly shared replicas (although any particular replica is
unaware of which other replicas it is commonly sharing with an unknown
replica).
= The sync schema includes both a plurality of predefined conflict handlers
available to all replicas, as well as the ability for user/developer defined
custom
conflict handlers. The schema also may also include three special "conflict
resolvers": (a) a conflict "filter" which resolves different conflicts in
different
ways based, e.g., (i) how to handle when same change unit changed in two
places,
(ii) how to handle when a change unit is changed in one place but deleted in
another; and (iii) how to handle when two different change units have the same
name in two different locations; (b) conflict "handler list" where each
element of
the list specifies a series of actions to attempt in order until the conflict
is
successfully resolved; and (c) a "do-nothing" log that tracks the conflict but
takes
no further action without user intervention.
= The sync schema and use of replicas enables a true distributed peer-to-peer
mutli-
master synchronization community. Moreover, there is no sync community type,
but the sync community exists simply as a value in the community field of the
replicas themselves.
= Every replica has its own metadata for tracking incremental change
enumeration
and storing state information for the other replicas that are known in the
sync
community.
= Change units have their own metadata comprising: a version comprising a
partner
key plus a partner change number; an Item/Extension/Relationship versioning
for
each change unit; Knowledge regarding the changes a replica has seen/received
from the sync community; a GUID and Local ID configuration; and a GUID
stored on a reference relationship for cleanup.
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IV. CONCLUSION
[0360] As the foregoing illustrates, the present invention is directed to a
storage
platform for organizing, searching, and sharing data. The storage platform of
the present
invention extends and broadens the concept of data storage beyond existing
file systems and
database systems, and is designed to be the store for all types of data,
including structured, non-
structured, or semi-structured data, such as relational (tabular) data, XML,
and a new form of
data called Items. Through its common storage foundation and schematized data,
the storage
platform of the present invention enables more efficient application
development for consumers,
knowledge workers and enterprises. It offers a rich and extensible application
programming
interface that not only makes available the capabilities inherent in its data
model, but also
embraces and extends existing file system and database access methods. It is
understood that
changes may be made to the embodiments described above without departing from
the broad
inventive concepts thereof. Accordingly, the present invention is not limited
to the particular
embodiments disclosed, but is intended to cover all modifications that are
within the spirit and
scope of the invention as defined by the appended claims.
[0361] As is apparent from the above, all or portions of the various systems,
methods,
and aspects of the present invention may be embodied in the form of program
code (i.e.,
instructions). This program code may be stored on a computer-readable medium,
such as a
magnetic, electrical, or optical storage medium, including without limitation
a floppy diskette,
CD-ROM, CD-RW, DVD-ROM, DVD-RAM, magnetic tape, flash memory, hard disk drive,
or
any other machine-readable storage medium, wherein, when the program code is
loaded into and
executed by a machine, such as a computer or server, the machine becomes an
apparatus for
practicing the invention. The present invention may also be embodied in the
form of program
code that is transmitted over some transmission medium, such as over
electrical wiring or
cabling, through fiber optics, over a network, including the Internet or an
intranet, or via any
other form of transmission, wherein, when the program code is received and
loaded into and
executed by a machine, such as a computer, the machine becomes an apparatus
for practicing the
invention. When implemented on a general-purpose processor, the program code
combines with
the processor to provide a unique apparatus that operates analogously to
specific logic circuits.
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