Interesting problem! My understanding is that you want to (1) find paths matching a particular pattern, and (2) add edges between the start and end vertices of the matched paths.
For (1), I implemented a pattern matcher for GraphX <https://github.com/ankurdave/spark/blob/PatternMatching/graphx/src/main/scala/org/apache/spark/graphx/lib/PatternMatching.scala> that iteratively accumulates partial pattern matches. I used your example in the unit test <https://github.com/ankurdave/spark/blob/PatternMatching/graphx/src/test/scala/org/apache/spark/graphx/lib/PatternMatchingSuite.scala> . For (2), you can take the output of the pattern matcher (the set of matching paths organized by their terminal vertices) and construct a set of new edges using the initial and terminal vertices of each path. Then you can make a new graph consisting of the union of the original edge set and the new edges. Let me know if you'd like help with this. Ankur <http://www.ankurdave.com/>
