Parsing XPath in XSLT?

XSL Friends,

What kinds of advice can you offer on the question of parsing XPath in XSLT?

I am currently having to interpret XPath or (more likely) an XPath
subset into an abstract representation that can be rewritten into
various forms. Naturally I would like to do this out of a parse tree
or the functional equivalent, represented in some sort of XML, since
serializing that back out is easy enough. It is producing that tree
that is a problem. I need a parser for XPath or if not for all of
XPath, then at least for my subset -- which includes namespaces. So
even if partial the model must expose names and namespaces to the
extent that a path rewriter can (for example) map into a new set of
namespace prefixes --

Any thoughts? Open source projects I should take a look at? Have the
community-standards initiatives captured any good work in this area?

Best regards,
Wendell

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