Gremlin is an interesting DSL, based on XPATH, for traversing graphs:
“Gremlin is a Turing-complete, graph-based programming language developed for key/value-pair multi-relational graphs called property graphs. Gremlin makes extensive use of XPath 1.0 to support complex graph traversals. Connectors exist to various graph databases and frameworks. This language has application in the areas of graph query, analysis, and manipulation.”
You can read the introduction and access the full set of presentation slides at dzone:
http://www.dzone.com/links/r/gremlin_a_graph_programming_language.html
The presentation shows a nice example using the Grateful Dead:
