The schema for the xpaths is missing from xsd/OpenDoPE, and after missing them for some time, I wrote one. Maybe its useful for anyone else. It adds a few restrictions in contrast to the one which can be directly derived from Xpaths.java and - on the other hand - drops those which I never met working with static (no questions) documents. Maybe its useful to someone else.
@Jason: wonder whether descrption (sic) and comments were ever used or should be removed. When designing anew, I'd replace then with elements for the sake of readability.
(edit 2011-07-20 07.03 UTC: dataBinding/@xpath must be xsd:string, not xsd:token; support double quotes for dataBindung/@prefixMappings.)