System and method for versioning data in a distributed data store

A system and method for versioning of atomic units of data (such as XML fragments) in a distributed data store are disclosed. The distributed data store may maintain a linear version history for each fragment, such that each has no more than one successor and one predecessor, with no implicit branching. An application programming interface may provide an explicit branching request (indicating an intent to merge modified data in a child branch into its parent branch), along with read, create, create-merge, and/or integrate requests. A reconciliation policy may be specified on a per-application basis, and may include automatic reconciliation using a callback function or interactive reconciliation, with inputs returned to the application. Writes to a minority side of a network partition may be refused unless an explicit branch is requested. Transactions may not be supported in client applications or may be supported through explicit branching. Transactions may be used internally.