BTW, I decided I'd see if there was an XPath library for Prolog (once my favorite programming language, and with some conceptual/ algorithmic similarity to XSLT

BTW, I decided I'd see if there was an XPath library for Prolog (once my favorite programming language, and with some conceptual/ algorithmic similarity to XSLT, I think, although XSLT has nothing like Prolog's backtracking). Turns out there is (at least) one: https://www.swi-prolog.org/pldoc/man?predicate=xpath%2f3 https://www.swi-prolog.org/pldoc/man?predicate=xpath%2f3. There's a comparison of Prolog and XSLT v1 here: https://arxiv.org/pdf/1912.10817v1 https://arxiv.org/pdf/1912.10817v1 (warning: poorly translated from the Russian original, and dated).