Another look at namespaces

[Rick Jelliffe]

From: Paul Prescod <paul at prescod.net>

>There is a world of difference between saying that a namespace *is a
>schema* and saying that there are a set of W3C specifications
(including
>XHTML) that have namespaces that have a one to one correspondance with
>schemas. It's like saying that "p" doesn't have to be defined in a DTD
>(because not every XML document has DTDs) but the *HTML* "p" *is*
>defined in a DTD (which has been the stance since HTML 2).

html:p
    1) is an element for generic paragraphs (semantics);
    2) is typically displayed as a block, and has sub-elements that are
typically displayed inline (presentation);
    3) is under the body element of an HTML document (schematic, but
defined from descendnt to ancestor).

That defines the html:p element type pretty completely, yet no grammar
(in the sense of content models on child elements) is involved. IMHO
DTDs/content-models actually disguise or fail to express the real schema
in html:p, which is more like the three points above.

What the content model gives is a way to validate a document, and a way
to construct a document after the deep structures
(classes/archetypes/extended containment/cohesion) have been abstracted
away or ignored. That is a good enough model for a DTD, but hardly a
good enough one for naming purposes; a name should express what a thing
is, and to say that HTML has three namespaces because it has 3 DTDs is
to get tripped up on a mere artifact of the modeling capabilities of
DTDs. (And in any case, a strictly conforming XHTML document has to have
a DOCTYPE declaration, so the namespace declarations don't actually
provide any information in the document than could be found there
already.)

Why should
    <html:p>blah<rick:dog />blah</html:p>
have to use a different namespace to
    <html:p>blah blah</html:p>
?  Lets allow extensibility from the start.


Rick Jelliffe



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