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Re: [xml-dev] Wikipedia on XML

Elliotte Rusty Harold schrieb am 21.08.2009 um 09:16:28 (-0700):
> On Fri, Aug 21, 2009 at 7:42 AM, Michael Kay<mike@saxonica.com> wrote:
> > A better approach might be to treat DTDs in the structure of the
> > article as co-equal with other schema languages, and mention in the
> > prose that for historical reasons they are given a special status in
> > the XML recommendation. That's a better reflection of the reality of
> > usage.
> No, I don't think that's sufficient. [DTDs] are fundamentally
> integrated into the design of an XML parser. They are not optional
> pieces one can ignore. Nor are they just a schema language either.
> They have noticeable effects on a document's infoset even in the
> absence of validation. Yes, in hindsight, this was a mistake; but it's
> not one we can ignore or sweep under the rug, much as we might wish
> things were otherwise. :-(

Why was that a mistake? The DTD is very useful. It provides a bag of
neat features that go a long way for authoring documents.

* uniting document instances under one DTD umbrella (external subset)
* physical document composition (external general entities)
* simple text replacement (internal parsed entities)
* document typing, validation and validity
* identifiers and references to identifiers
* parametrizing at the instance level (parameter entities)
* default values

The only thing that does not reveal its usefulness to me is the funny
NDATA/NOTATION construct. (Maybe it was useful in the past, maybe it is
still useful for situations I'm unaware of.)

So given the rest is pretty useful and the DTD syntax and functionality
is really easy to learn and understand, why should it have been a
mistake to include this great bag of features in XML?

Michael Ludwig

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