[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Statement from HTML WG
> From: Steven Pemberton <steven@c...> > Subject: XHTML: One Namespace or Three? > > Executive summary: Namespaces are used by software to distinguish what > is contained in a piece of markup. ... Actually, that's the role assigned to DTDs. "What is contained" is a content model style constraint. Namespaces are only used to disambiguate the markup itself, as you said later -- "table" as in XHTML versus a kind of furniture, "frame" as in XHTML versus door (or window...) construction. > What are Namespaces > > ... according to the Namespace recommendation, Namespaces are used to > disambiguate different vocabularies, without saying where those > vocabularies come from. ... Which says nothing about placing constraints on how those vocabularies are used. DTDs address such constraints, and they aren't synonymous with definitions of vocabularies. This is shown by the HTML spec, which talks about "one language" and yet has "three DTDs" used to provide three different kinds of constraint about how its vocabulary is used. (Also by common usage -- "HTML" does not generally care about such nuances.) > History > > After publishing the draft we received two comments (though without > technical argumentation) saying that there should only be one > namespace. Odd -- I knew of at least three, each with technical argumentation. Those were highlighted on the plenary (back when I had regular access to that sort of information). And I seem to recall that they were not the only comments to that effect, but only the ones which seemed most clearly expressed. > Using Namespaces > > ... in a fragment such as the following: > > <notes> > <p xmlns='http://www.w3.org/TR/xhtml1/strict'> > This is also available > <a href="http://www.w3.org/">online</a>. > </p> > </notes> > > the namespace is the only mechanism available for identifying the > vocabulary intended. True. And DTDs are the only mechanism available for specifying any content model restrictions that may be desired. It has been made abundantly clear that developers expect schema mechanisms to support content model restrictions when combining vocabularies ... and to do so without depending on specific prefixes. Likewise, it is clear that until such schema mechanisms exist, people WILL use DTDs for at least some cases of vocabulary combination, by hardwiring prefixes. (Not all -- "some", hence the desire to see progress on schemas.) The point has also been raised that in the example above, the "p" element would often need to contain inline elements from specialized vocabularies. Using a namespace to identify a content model (instead of a separate DTD or schema) effectively precludes vocabulary re-use through combination, which is quite contrary to the goals I've understood for XML, namespaces, or related technologies. - Dave 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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