- From: <bugzilla@wiggum.w3.org>
- Date: Tue, 14 Apr 2009 23:05:14 +0000
- To: www-xml-schema-comments@w3.org
http://www.w3.org/Bugs/Public/show_bug.cgi?id=5023
Michael Kay <mike@saxonica.com> changed:
What |Removed |Added
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CC| |mike@saxonica.com
--- Comment #9 from Michael Kay <mike@saxonica.com> 2009-04-14 23:05:13 ---
If we're advising users which of these mechanisms to use under which
circumstances, then I think there are two observations I would want to make:
(a) it's a lot easier for an implementation to enforce identity constraints and
CTA while processing the document in a streaming manner than it is to enforce
assertions
(b) using a specialized mechanism such as identity constraints rather than a
general mechanism like assertions may result in a more focused and intelligible
error message when the condition is violated. For example, the assertion
test="count(//empno)=count(distinct-values(//empno))" is unlikely, if violated,
to result in an error message that tells the user how many duplicate employee
numbers there are, which numbers are duplicated, or where to look for them in
the instance document. I think the same is probably true of other reasonable
ways of expressing this constraint, such as test="every $a in //empno, $b in
//empno satisfies $a is $b or $a ne $b"
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Received on Tuesday, 14 April 2009 23:05:22 UTC