[xquery-talk] Function for determining one XPath as subset of another

[daniela florescu]

> 
> It seems to be a long-standing tradition that computer scientists, when asked to prove a difficult conjecture C, respond by giving a proof for a simplified conjecture C'. While this might lead to progress in the long run, and enables them to get papers published in the academic literature, it is totally useless to practical engineeers who want to know whether they can safely rely on C.

Michael,


what you say is nice and true. 

However given that:
1. path expressions point (syntactically hence esemantically) into XQuery’s expressions
2. XQuery expression language is Turing complete
3. Subsumption for a Turing complete language is undecidable.

Well, I can hardly see a way to decide this problem other then by introducing SOME restrictions
of some sort… but of course some restrictions that would not nullify the original problem all together
and make the solution useless.

Best,
Dana