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Re: Why this restriction? (was Constraining a "mixed" mixed co

• To: xml-dev@l...
• Subject: Re: Why this restriction? (was Constraining a "mixed" mixed content model
• From: richard@i... (Richard Tobin)
• Date: Mon, 12 Sep 2005 17:26:24 +0100 (BST)
• Cc:
• In-reply-to: <1126536990.29765.242713147@w...>
• Organization: HCRC, University of Edinburgh

In article <1126536990.29765.242713147@w...> you write:

>Now, to comment on your reply, which does seem to be right (where in
>the XML 1.0 spec does it specifically say DTDs are not allowed to
>constrain as I'd like it to?)

  http://www.w3.org/TR/REC-xml/#sec-mixed-content

>From a philosophical perspective, I find it sort of perplexing why
>there is this seeming limitation imposed upon DTDs.

It's a consequence of XML being a simplified subset of SGML.

>It would seem, in the case I ask about, that a future version of XML
>could easily, and without breaking current XML documents and DTDs,
>give DTDs greater power at specifying constraints.

There is unlikely ever to be a future version of XML that changes
DTDs.  No-one wants to work on such a specification, and no-one wants
to implement it.

A more likely change (though still unlikely I think) is the complete
removal of DTDs.

If you want to constrain the content of your XML documents in ways that
DTDs don't support, consider the various schema tools.

-- Richard

• References:
  • Why this restriction? (was Constraining a "mixed" mixed content model (XHTML <div>))
    • From: "Mark O. Zorro" <markozorro@f...>

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