- From: <bugzilla@wiggum.w3.org>
- Date: Wed, 15 Apr 2009 15:32:27 +0000
- To: www-xml-schema-comments@w3.org
http://www.w3.org/Bugs/Public/show_bug.cgi?id=5023 --- Comment #12 from Noah Mendelsohn <noah_mendelsohn@us.ibm.com> 2009-04-15 15:32:27 --- Michael Kay writes: > There are many constraints that people want to > express that require the full power of XPath. I > don't regard it as a "concern" that people are > able to express constraints that are expensive to > evaluate - it's their decision. Fair enough, but that doesn't quite capture my concern. I worry some that, since XPath in general doesn't stream without a lot of hard work, many implementors might not do an efficient job even with the simple XPaths that do. So, instead of the situation you describe, in which a smart user knows which paths will stream and which won't, even the simple ones will run much slower than they might. That said: it's certainly the case that nobody would be dumb enough to use space that's the square of the document size just to evaluate @a > @b, even though doing so might be tempting for: test="every $a in //empno, $b in //empno satisfies $a is $b or $a ne $b" So I think your point holds to a significant degree anyway. It will be unfortunate if implementations don't take the trouble to notice and optimize the simple common cases. Noah -- Configure bugmail: http://www.w3.org/Bugs/Public/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the QA contact for the bug.
Received on Wednesday, 15 April 2009 15:32:39 UTC