Microsoft Sync Framework
Encyclopedia
Microsoft Sync Framework is a data synchronization platform from Microsoft
that can be used to synchronize data across multiple data stores. Sync Framework includes a transport-agnostic architecture, into which data store-specific synchronization providers, modelled on the ADO.NET
data provider API, can be plugged in. Sync Framework can be used for offline access to data, by working against a cached set of data and submitting the changes to a master database in a batch, as well as to synchronize changes to a data source across all consumers (publish/subscribe sync) and peer-to-peer
synchronization of multiple data sources. Sync Framework features built-in capabilities for conflict detection - whether data to be changed has already been updated - and can flag them for manual inspection or use defined policies to try to resolve the conflict. Sync Services includes an embedded SQL Server Compact
database to store metadata
about the synchronization relationships as well as about each sync attempt. The Sync Framework API are surfaced both in managed code
, for use with .NET Framework
applications, as well as unmanaged code, for use with COM
applications. It was scheduled to ship with Visual Studio 2008. in late November 2007.
The Sync Framework runtime provides synchronization functionality, without being tied to any data store or data transport protocols. By providing data source specific synchronization providers, any data source can be supported. For example, using proper synchronization providers, files can be synchronized across computers, project updates synchronized across project participants, or media synchronized across devices. Sync Framework ships with three providers: Microsoft Sync Services for ADO.NET, Sync Services for File Systems, and Sync Services for SSE. Sync Services can be used to synchronize devices by supplying providers for the device. Similarly, PIM software such as Microsoft Office Outlook and media libraries such as Windows Media Player
can also be supported by providing suitable providers.
The providers are used to enumerate the items in a data store, each identified by an Item ID. In addition, they also have to maintain synchronization metadata and the state of the data store, so that changes can be enumerated quickly. The metadata is maintained for every instance of the data store (replica) that the provider is attached to. The metadata maintained includes the replica ID, tick count (representing progression in time), conflict log, tombstone log
, and the set of the changes the data store has seen (knowledge). A replica ID and tick count pair makes up a
database to store the metadata on a per-provider basis.
The Sync Services API operates by creating a synchronization session, represented by a
Microsoft Sync Services for ADO.NET is the synchronization provider for synchronizing across databases using ADO.NET
. ADO.NET
Datasets are synchronized between the source and the destination, which are then persisted to a database server. It can also support data sources other than a relational database
, like an XML database
or web service
as long as a proxy is provided to abstract the data source and a data provider is available for the proxy.
The Sync Services for ADO.NET
provider is intended for use in offline applications, where data from the central database is cached locally. The application works against the cached data, and the changes are uploaded in a batch. In addition, the provider can also be used for collaborative applications, where each application will work against its local dataset, which will be synchronized periodically in a peer-to-peer
manner with the other participants. Locally, the datasets can be stored either by using the SQL Server Compact
database or any other database server supporting ADO.NET. Sync Services for ADO.NET allows incremental change tracking, which allows only the changes to be replicated rather than replicating the entire copy.
manner. Neither Sync Framework or the Sync Services for File Systems provider perform any authentication before accessing the files; so any authentication is the job of the application using the Sync Framework API. The files are transferred without encryption. To use encryption in transit, custom providers that uses an encrypted TCP connection needs to be used. The Sync Services for File Systems provider also supports static filters to exclude files based on wildcard
s or attributes. In the first release, however, the Sync Services for File Systems provider does not sync either NTFS security descriptor
s or Alternate Data Streams.
, either in RSS
or ATOM
formats, which can then be subscribed to by interested parties. The provider can also be used to extract items from a FeedSync feed and merge the changes back to the data store. Sync Services for FeedSync uses another provider to connect to the data store.
Sync Services for FeedSync provides services that can be used to help synchronize the data of a replica with RSS and Atom feeds. (A replica is a particular repository of information to be synchronized.) By using the FeedSync producer service, a synchronization application can work with a synchronization provider to create a list of items from a replica and put them in an RSS or Atom XML stream. These items can then be published to interested subscribers. Similarly, the FeedSync consumer service helps a synchronization application take an input RSS or Atom XML stream, extract items from it, and then use a synchronization provider to apply only the appropriate changes to a replica. Because Sync Framework underlies the exchange of feed items, two feeds can be cross-subscribed and easily synchronized with one another as peers in a synchronization community. (A synchronization community is a set of replicas that keep their data synchronized with each other.)
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
that can be used to synchronize data across multiple data stores. Sync Framework includes a transport-agnostic architecture, into which data store-specific synchronization providers, modelled on the ADO.NET
ADO.NET
ADO.NET is a set of computer software components that programmers can use to access data and data services. It is a part of the base class library that is included with the Microsoft .NET Framework. It is commonly used by programmers to access and modify data stored in relational database systems,...
data provider API, can be plugged in. Sync Framework can be used for offline access to data, by working against a cached set of data and submitting the changes to a master database in a batch, as well as to synchronize changes to a data source across all consumers (publish/subscribe sync) and peer-to-peer
Peer-to-peer
Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
synchronization of multiple data sources. Sync Framework features built-in capabilities for conflict detection - whether data to be changed has already been updated - and can flag them for manual inspection or use defined policies to try to resolve the conflict. Sync Services includes an embedded SQL Server Compact
SQL Server Compact
Microsoft SQL Server Compact is a compact relational database produced by Microsoft for applications that run on mobile devices and desktops. Prior to the introduction of the desktop platform, it was known as SQL Server for Windows CE and SQL Server Mobile Edition...
database to store metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
about the synchronization relationships as well as about each sync attempt. The Sync Framework API are surfaced both in managed code
Managed code
Managed code is a term coined by Microsoft to identify computer program code that requires and will only execute under the "management" of a Common Language Runtime virtual machine ....
, for use with .NET Framework
.NET Framework
The .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and supports several programming languages which allows language interoperability...
applications, as well as unmanaged code, for use with COM
Component Object Model
Component Object Model is a binary-interface standard for software componentry introduced by Microsoft in 1993. It is used to enable interprocess communication and dynamic object creation in a large range of programming languages...
applications. It was scheduled to ship with Visual Studio 2008. in late November 2007.
Architecture
Windows Media Player
Windows Media Player is a media player and media library application developed by Microsoft that is used for playing audio, video and viewing images on personal computers running the Microsoft Windows operating system, as well as on Pocket PC and Windows Mobile-based devices...
can also be supported by providing suitable providers.
The providers are used to enumerate the items in a data store, each identified by an Item ID. In addition, they also have to maintain synchronization metadata and the state of the data store, so that changes can be enumerated quickly. The metadata is maintained for every instance of the data store (replica) that the provider is attached to. The metadata maintained includes the replica ID, tick count (representing progression in time), conflict log, tombstone log
Tombstone (programming)
Tombstones are a mechanism to detect dangling pointers that can appear in certain computer programming languages, e. g. C, C++ and assembly languages, and to act as a containment to their dangerous effects....
, and the set of the changes the data store has seen (knowledge). A replica ID and tick count pair makes up a
version and encodes the state of the data store until that time. Sync Framework defines a set of operation for the Knowledge object for a replica: Contains which determines if the store contains a specified change, Union to merge two knowledge sets, Project to project out the knowledge for a subset of the items, and Exclude to create a new knowledge set without the changes for a subset of the items. The metadata is managed by the metadata storage service which uses an in-process SQL Server CompactSQL Server Compact
Microsoft SQL Server Compact is a compact relational database produced by Microsoft for applications that run on mobile devices and desktops. Prior to the introduction of the desktop platform, it was known as SQL Server for Windows CE and SQL Server Mobile Edition...
database to store the metadata on a per-provider basis.
The Sync Services API operates by creating a synchronization session, represented by a
Session object. A synchronization session synchronizes data across two synchronization providers - one for the source data store and the other for the destination. Instances of both the providers are passed to the Session object. During a synchronization session, the destination provider sends the knowledge set of the store. The source provider compares the knowledge of the destination with the change set in the source to enumerate the changes and then transfer it to the destination. The destination provider makes sure the changes are not conflicting and merges the changes and updates the knowledge.- Snapshot sync (download-only sync): The data in the data source (or a subset of it) is synchronized with clients.
- Upload-only sync: Data in the client is merged to the source replica.
- Bidirectional sync: Both the data sources can be modified independently and changes are synchronized with each other. An n-level sync is achieved by performing multiple bidirectional synchronizations.
Sync Services for ADO.NET
ADO.NET
ADO.NET is a set of computer software components that programmers can use to access data and data services. It is a part of the base class library that is included with the Microsoft .NET Framework. It is commonly used by programmers to access and modify data stored in relational database systems,...
. ADO.NET
ADO.NET
ADO.NET is a set of computer software components that programmers can use to access data and data services. It is a part of the base class library that is included with the Microsoft .NET Framework. It is commonly used by programmers to access and modify data stored in relational database systems,...
Datasets are synchronized between the source and the destination, which are then persisted to a database server. It can also support data sources other than a relational database
Relational database
A relational database is a database that conforms to relational model theory. The software used in a relational database is called a relational database management system . Colloquial use of the term "relational database" may refer to the RDBMS software, or the relational database itself...
, like an XML database
XML database
An XML database is a data persistence software system that allows data to be stored in XML format. This data can then be queried, exported and serialized into the desired format.Two major classes of XML database exist:...
or web service
Web service
A Web service is a method of communication between two electronic devices over the web.The W3C defines a "Web service" as "a software system designed to support interoperable machine-to-machine interaction over a network". It has an interface described in a machine-processable format...
as long as a proxy is provided to abstract the data source and a data provider is available for the proxy.
The Sync Services for ADO.NET
ADO.NET
ADO.NET is a set of computer software components that programmers can use to access data and data services. It is a part of the base class library that is included with the Microsoft .NET Framework. It is commonly used by programmers to access and modify data stored in relational database systems,...
provider is intended for use in offline applications, where data from the central database is cached locally. The application works against the cached data, and the changes are uploaded in a batch. In addition, the provider can also be used for collaborative applications, where each application will work against its local dataset, which will be synchronized periodically in a peer-to-peer
Peer-to-peer
Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
manner with the other participants. Locally, the datasets can be stored either by using the SQL Server Compact
SQL Server Compact
Microsoft SQL Server Compact is a compact relational database produced by Microsoft for applications that run on mobile devices and desktops. Prior to the introduction of the desktop platform, it was known as SQL Server for Windows CE and SQL Server Mobile Edition...
database or any other database server supporting ADO.NET. Sync Services for ADO.NET allows incremental change tracking, which allows only the changes to be replicated rather than replicating the entire copy.
Sync Services for File Systems
The Sync Services for File Systems provider is used to synchronize two file system locations, which can either be local folders or network shares. In addition to mirroring new files, changes to existing files are also synchronized. Changes to files are detected by using timestamps, or optionally, by hashing the file contents. Conflicting changes to the same file are detected and can be set to be automatically resolved. For conflicting updates to a same file, the newer edit will be kept. If a file is deleted in one replica but updated in another, the update will take precedence over the delete. If two files with different content are created with the same name across two replicas, during the sync operation, the one created later will be persisted. If a rename operation caused the files to get the same name, both are retained by renaming one of them. Any deletes can be configured to move the file to the Recycle Bin, so that it can be recovered if necessary. The Sync Services for File Systems provider also provides a preview mode which enumerates the actions that will be taken for a sync operation, without actually performing the operations, with a view to letting the users review the changes that will be made. The synchronization is performed in a peer-to-peerPeer-to-peer
Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
manner. Neither Sync Framework or the Sync Services for File Systems provider perform any authentication before accessing the files; so any authentication is the job of the application using the Sync Framework API. The files are transferred without encryption. To use encryption in transit, custom providers that uses an encrypted TCP connection needs to be used. The Sync Services for File Systems provider also supports static filters to exclude files based on wildcard
Wildcard character
-Telecommunication:In telecommunications, a wildcard character is a character that may be substituted for any of a defined subset of all possible characters....
s or attributes. In the first release, however, the Sync Services for File Systems provider does not sync either NTFS security descriptor
Security descriptor
Security descriptors are data structures of security information for securable Windows objects, that is objects that can be identified by a unique name...
s or Alternate Data Streams.
Sync Services for FeedSync
The Sync Services for FeedSync provider can be used to help synchronize replicas by creating a FeedSync enabled feedWeb feed
A web feed is a data format used for providing users with frequently updated content. Content distributors syndicate a web feed, thereby allowing users to subscribe to it. Making a collection of web feeds accessible in one spot is known as aggregation, which is performed by an aggregator...
, either in RSS
RSS
-Mathematics:* Root-sum-square, the square root of the sum of the squares of the elements of a data set* Residual sum of squares in statistics-Technology:* RSS , "Really Simple Syndication" or "Rich Site Summary", a family of web feed formats...
or ATOM
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
formats, which can then be subscribed to by interested parties. The provider can also be used to extract items from a FeedSync feed and merge the changes back to the data store. Sync Services for FeedSync uses another provider to connect to the data store.
Sync Services for FeedSync provides services that can be used to help synchronize the data of a replica with RSS and Atom feeds. (A replica is a particular repository of information to be synchronized.) By using the FeedSync producer service, a synchronization application can work with a synchronization provider to create a list of items from a replica and put them in an RSS or Atom XML stream. These items can then be published to interested subscribers. Similarly, the FeedSync consumer service helps a synchronization application take an input RSS or Atom XML stream, extract items from it, and then use a synchronization provider to apply only the appropriate changes to a replica. Because Sync Framework underlies the exchange of feed items, two feeds can be cross-subscribed and easily synchronized with one another as peers in a synchronization community. (A synchronization community is a set of replicas that keep their data synchronized with each other.)