- From: <bugzilla@wiggum.w3.org>
- Date: Mon, 07 Dec 2009 14:53:31 +0000
- To: www-xml-schema-comments@w3.org
http://www.w3.org/Bugs/Public/show_bug.cgi?id=8444 --- Comment #2 from C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com> 2009-12-07 14:53:31 --- As Michael Kay has observed, the reformulation of the Unique Particle Attribution in 1.1 (the so-called 'weakened wildcard' change) does make it legal for a wildcard particle to compete with an element particle in a content model, and thus for an optional element particle to precede a wildcard in a sequence. In 1.0 it is not allowed for wildcard and element particles to compete, and so an optional element particle cannot be followed in a sequence by a wildcard. So in 1.0 the solution to the problem needs to take place on a different layer of the design: if you don't want first-generation apps to break when they see content that is not valid against the first-generation schema, then write them to accept invalid input and do the best they can with it. (HTML has prospered fairly well with this recipe.) Or rewrite the illegal content model with an equivalent content model that is legal. In the example given, the content models desired for the second and third generation apps (the ones shown, plus an additional repeating wildcard) seem at first glance to accept the same language as the content model given for the first-generation app. The differences thus appear to have at most a rhetorical or documentary function. Am I missing something? The Unique Particle Attribution constraint certainly makes some regular languages inexpressible, and I continue to believe that it should never have been made part of XSD and that it should be eliminated at the first opportunity. But the simple wildcard problems described here and in some other discussions of versioning don't seem to involve languages that cannot be expressed in XSD 1.0 content models; they involve, as far as I can see, only a dissatisfaction with the expression prescribed for those languages by XSD 1.0. -- 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 Monday, 7 December 2009 14:53:34 UTC