> Well, so, to continue, let's assume that there are no user-defined > functions, and in fact the only thing we want to proof is select+filter, > where a filter is limited to the default operators. From that is it follows > that > > -path1: > select-child-nodes-by-name(select-child-nodes-by-name($context,'x'),'w') > -path2: select-descendant-nodes-by-name($context,'w')
Just to complete this: The predicate must not be numeric (//w[1] is not equivalent to /descendant::w[1]). > Op woensdag 27 januari 2016 heeft daniela florescu <[email protected]> het > volgende geschreven: >> >> > >> > 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 > > > > -- > > W.S. Hager > Lagua Web Solutions > http://lagua.nl > > > > _______________________________________________ > [email protected] > http://x-query.com/mailman/listinfo/talk _______________________________________________ [email protected] http://x-query.com/mailman/listinfo/talk
