Dick Lipton had a project on succinct graph specifications and a Ph.D. student, Hana Galperin, who wrote her Ph.D. thesis on this topic. We have refined this technology during the last 7 years and is used in several compiler projects including in an industrial project for writing compilers for application specific languages.
Traversals are ubiquitous.
But most of the time you traverse entire clusters of objects. Supporting the visitor pattern is what we do very well. We also have an abstract syntax description language similar to yours. Mitchell Wand told me about your interesting Zephyr project. I'm one of the students reponsible for the ASDL tools.