[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: RFP: Namespace URI for HTML
[I'll answer this one question, and then will try to shut up again.] Sebastian Schnitzenbaumer writes: > > Then why not allow the html:version attribute on *any* HTML > > element? Then you can specify version information for subtrees > > as well as for an entire HTML document. > > This mechanism would then be similar to namespaces in design. Well, in scope, at least... > You are suggesting that the namespace is the highest level of > hierarchie, and every XML grammar that has multiple variants shall > introduce its own mechanism to distinguish the variants as the > second level below namespaces. Only if they need to. The problem is that there are at least two different kinds of information needed about an element or attribute name: 1. What is the major group that this belongs to (HTML, TEI, DocBook, etc.)? 2. What is the special variant (version/flavour) that this belongs to (XHTML 1.0 strict, etc.)? No matter how we slice it, *one* of these is going to be easy for programs to discover and one of them is going to be harder. Using a single XHTML Namespace URI and an html:version attribute makes #1 easy and #2 only slightly more difficult; using multiple XHTML Namespaces and complex schema/RDF constructions makes #2 easy but #1 relatively much more difficult. So the question is not whether #1 or #2 should be omitted (both are needed), but which one most applications will care about. My guess is that most applications will care about #1, and that applications that need #2 will be sophisticated enough anyway that checking another attribute won't be a big deal. > XHTML is a language with quite some history. I a few years, it is > likely that other XML grammars will have the same situation like > HTML (SMIL, for instance). I feel unconfortable introducing such a > mechanism now just for XHTML where it will be likely that a similar > mechanism will be needed in different languages as well. In the > end, the version attribute will be used in conjunction with the > xmlns attribute for many popular languages. So then why have two > mechanisms, where one is global and the other one is always > language-specifc, but both are in the same space. There's good precedent -- think of Perl packages, for example, which have a single, persistent package name across all versions and then use a conventional $VERSION attribute, as in the following example: package XML::Writer; $VERSION = "0.2"; All well-behaved Perl packages use the $VERSION attribute the same way. That way, applications written to work with XML::Writer 0.1 will continue to work with XML::Writer 0.2, but applications that need to be sure can check the $XML::Writer::VERSION attribute. In other words, this suggestion is well-proven in major-scale, real-world implementations (last I heard, Perl was still the driving engine behind Amazon.Com and Yahoo!, for example). All the best, David -- David Megginson david@m... http://www.megginson.com/ xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1 To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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