Re: keyrefs

> > Since Schematron is built on top of XSLT, as soon as XPath support
> > the PSVI this is exactly what we'll be able to do. And if we don't
> > want to wait for the next XPath we can use Francis Norton's new
> > "poor-man's PSVI...".
>
> Yes. I was more thinking of perhaps something being incorporated in
> the next version of XML Schema that would allow us to represent things
> like 'this attribute or that element' without bugging out to
> Schematron or RELAX NG.

This would be very useful indeed. Even though it's quite easy to combine
the schema languages it does of course introduce extra steps in the
validation process so if Schematron-like rules could be built into the XML
Schema language itself that would be very good. However, I'm not sure how
feasible this really is. I know that some form of co-occurence constraints
are the list for the next version but who knows when that will happen.

> >> Mixing the modular style of XML Schema with XPath is pretty nasty
> >> (although perhaps XPath 2.0 will help, if it supports testing of
> >> user-defined types).
> >
> > I think it will but I'm not entirely sure.
>
> I guess we'll have to wait for the XPath WD :) The XQuery/XPath data
> model includes types, but this doesn't necessarily mean that you're
> able to *test* the type of an element. For example, the data model
> might just include types so that it's possible to describe the
> mechanism by which an XPath processor works out which primitive type
> an element has as a value (just as the data model describes the Base
> URI of a node but XPath has no way of actually accessing that as a
> string). The XQuery/XPath operators document doesn't have anything
> about user-defined types that I can remember, so if there is anything
> my guess is it will be an axis.

Hmm, I haven't actually looked at the spec for the next XPath but I was
hoping it would have support for the PSVI. But then again I'm not even
sure what stage the PSVI is in so I guess only time will tell what's going
to happen.

Cheers,
/Eddie

Received on Monday, 12 November 2001 18:31:11 UTC