Sync Framework Glossary

This glossary lists and defines Microsoft Sync Framework concepts and terminology.



The process of sending changes in small groups instead of in a one-shot transfer of the data in its entirety.

change unit

The minimal unit of change tracking in a store. Change units are contained in an item, such as name and address fields in a contact item. In change propagation, only the change units that are changed must be sent. In conflict detection, only changes to the same change unit are considered a conflict.


A service, application, or device that wants to integrate into the Sync Framework architecture.

clock vector

A replica key/tick count pair that represents updates to a replica. Any change that occurs between 0 and the tick count is contained in the vector.

conflict resolution method

The method that is used to determine which change is written to the store if there is a conflict. Typical conflict resolution methods are as follows: last writer wins, source wins, destination wins, custom, or deferred. For custom resolution, the resolving application reads the conflict from the conflict log and selects a resolution. For deferred resolution, the conflict is logged together with the conflicting change data and the made-with knowledge of the change.

consistency unit

The minimal unit of consistency. Because all changes that have the same consistency unit are sent together, synchronization can never be interrupted when only part of a consistency unit is applied.

flexible identifier

An identifier that is assigned to various synchronization entities, such as replicas. The identifier can be of fixed or variable length.

global identifier

A unique identifier that is assigned to a data item. The identifier must be unique across all clients. A global identifier is a flexible identifier and so can be any format. However, the format is typically a GUID and an 8-byte prefix.


A unit of data or metadata that is being synchronized. A typical item of data might be a file or record, whereas a typical item of metadata might be a knowledge item.

made-with knowledge

The current knowledge of a source replica, to be used in conflict detection. Made-with knowledge answers the question: What did you know when you made these changes?

learned knowledge

The current knowledge of a source replica about a specific set of changes, and the logged conflicts of that replica. Learned knowledge answers the question: What will I learn when I apply this batch of changes?


The metadata that is maintained by each participant that describes all the changes it has seen. In its simplest form, known as a watermark, a knowledge item is a clock vector that consists of pairs of replica keys and replica tick counts.


A provider and its associated replica.


A set of continuous item identifiers to which the same clock vector applies. A range is represented by a starting point, an ending point, and a clock vector that applies to all IDs that are in between.


A particular repository of information to be synchronized.

replica ID

A value that uniquely identifies a replica.

replica key

A 4-byte value that maps to a replica ID in a replica key map.


The set of data that is being synchronized.

synchronization application

A software component, such as a personal information manager or music database, that hosts a synchronization session and invokes synchronization providers to synchronize different data stores.

synchronization community

A set of replicas that keep their data synchronized with one another.

synchronization provider

A software component that represents a replica for synchronization. When acting as a source, it enumerates changes from its replica. When acting as a destination, it applies changes to its replica. For data format mismatch, it performs any necessary schema transformation.

synchronization session

A unidirectional synchronization in which the source provider enumerates its changes and sends them to the destination provider, which applies them to its store.

tick count

A monotonically increasing number that is specific to a replica and combined with a replica key to make a version.


A marker that is used to represent an item that has been deleted. A tombstone is used to track deleted items and prevent their reintroduction into the synchronization community.


Metadata that identifies a revision to an item. It consists of the replica key and the replica tick count for the item.

See Also