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   RE: [xml-dev] What is the name of a document's "type"?

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There is no single notion of document type. You can define a number of
classification criteria that you apply to documents, based on the namespaces
they use, the schemas they conform to, the name of the top-level element,
and so on, and you can call any one of these the "document type" if that
makes sense in your application area.

Remember that in the real world, types are rarely mutually exclusive.
(History and Biography overlap, a fact which most bookshops choose to
overlook.) You can create a document that is both a valid XHTML document and
a valid XSLT stylesheet.

Mike Kay

> -----Original Message-----
> From: Bill Lindsey [mailto:bill@b-bop.com]
> Sent: 25 January 2002 23:01
> To: xml-dev@lists.xml.org
> Subject: [xml-dev] What is the name of a document's "type"?
> It's a question I've frequently been asked, and I haven't
> been able to come up with any answer that I feel
> confident of.  Still, I think it's a useful question
> to answer.
> In my day job, writing software for a native XML database,
> I get customer requests such as "list the docbook documents".
> If they've configured our database to know about the public
> ID for their local modifications to the DTD, and if they
> include a DOCTYPE declaration when they store the document,
> and if they don't do anything egregious with the internal
> subset, we can do that.
> If the customer request is "list the XSLT stylesheets"
> then DTD's won't do.  I'll need to look at the namespace
> qualified root element name.
> If the request is "list the RDDL documents", the root element
> name by itself won't do. I can hope they've included a DOCTYPE
> declaration, or see if they've got an xhtml root element,
> and some elements from the RDDL namespace, and hope
> that there aren't any elements from some other namespaces
> that modify the conventional meaning of RDDL elements.
> I could answer all of the above requests by requiring
> out-of-band signalling of "type information", but that
> complicates interfaces and introduces the potential for
> inconsistancies between the instance and the metadata.
> Note that in the above examples, all I need to know
> is the answer to the question "Is this document an
> instance of type 'x'?"  I don't need or necessarily
> want the document or type 'x' to automagically tell
> me how I should process, or validate it.  I can figure
> that out for myself, thank-you-very-much, based on
> what it is I'm  trying to do with it at that particular
> moment.
> What I (think I) want is a reliable, minimally intrusive
> mechanism to associate documents (and perhaps elements) to
> with some type name(s).
> I think the most successful solution would be one that
> can give the most specific answer to 1) "what is this
> thing's type name" and accurately answer 2) "is this
> thing an instance of the type named 'x'?" while
> having the least to say about what types "mean" or
> imposing any particular processing model or information
> set rewriting.
> While architectural forms appear to do a good job of
> answering the two questions, I'm having trouble
> with the special lenses one needs to see the instances.
> Hoping to learn,
> Bill
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