TXL: Tree Transformation Language

I essentially think of Decl macros or maps or whatever as falling into two categories: first is the text expression of a template, but the other works on tree structures.

Googling on "tree transformation" is a useful exercise, and five minutes perusal finds me two good links: TXL (the tree transformation language) is precisely what I want to be able to do (with a rule-based approach), and then there's an interesting paper ("A Language for Bidirectional Tree Transformations") by the Unison guys at UPenn about reversible lenses that act between tree structures, which is of course my map concept. (I should probably read everything they're doing.)

So those need to be read carefully. I'm sure there's more.