Re: [xsl] [XPath] matching elements which satisfy a specific content model

[Tobias Reif <tobiasreif@xxxxxxxxxxxxx>]

Michael Kay wrote:

>> But I'm proposing a content-model() function whose only reason for
>> existence is simplification and terseness.
>
> At one stage XQuery did this. It had its own grammar for describing
> content models, with all the paraphernalia of lists and unions and
> sequences, and it allowed you to test whether a particular element
> conformed to a particular content model (so-called "structural
> typing").

Sounds great; anything online?

> Everyone came down on them like a ton of bricks,

:(

> saying W3C
> already had a language for doing that and it was called XML Schema.

They don't seem to like the principle called TIMTOWTDI ... and the one 
where one chooses the least powerful tech/lang for each task. (simple 
grammar for simple models, full-blown schema lang for complex models)

> So
> they took it all out, leaving just the ability to test whether a
> particular element is a valid instance of a particular schema-defined
> type: "named typing". The result is vastly simpler,

... inside the pattern, but not overall, since the content is described 
elsewhere (and I wouldn't call WXS "vastly simple").

> but it does assume
> that you want to define your content models in a schema and not in a
> stylesheet - a reasonable assumption, in my view.

I'd prefer choice. This way, the "structural typing"/content-model() 
could stay very terse and simple, and then there would be "named typing" 
 for all the complex content models which are better described with WXS 
or RNG.

But again: What you describe (XSLT2 + XML Schemas(WXS/RNG)) will 
probably be a lot more fun than XSLT + XPath1.0 for describing 
(matching/testing) content models.

Tobi

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