I am working with a team that edits large DAGs represented as single files. Currently we are unable to work with multiple users concurrently modifying the DAG.

Is there a tool (somewhat like the Eclipse SVN plugin) that can do do revision control on the file (manage timestamps/revision stamps) to identify incoming/outgoing/conflicting changes (Node/Link insertion/deletion/modification) and merge changes just like programmers do with source code files?

The system should be able to do dependency management also. E.g. an incoming Link must not be accepted when one of the two Nodes is absent. That is, it should not "break" the existing DAG by allowing partial updates.

If there is a framework to do this using generic "Node" and "Link" interfaces?

Note: I am aware of Protege and its plugins. They currently do not satisfy my requirements.