Tools for XML based Directed Graphs?

Visual Studio 2010 has this feature called Directed Graph Documents (files with a dgml extension). It can be used to show relationships between objects similar to UML. I was able to play with it during the VS2010 beta. The version I now have (VS2010 pro) doesn't have this functionality and I don't have access to th开发者_Go百科e Ultimate or Architect versions.

Is there a similar XML based directed graph technology you can recommend?

Five months without an answer, so I guess the answer as of now is...

No, there are no tools other than Visual Studio 2010 Ultimate or Architect that can work with Directed Graph Documents. VS2010 Premium can read dgml documents, but not edit them.