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Re: Types and Context

Hi Jonathan,

Sorry - rereading, I see I missed one of your points:

> see that this might be implemeneted in a schema language neutral
> fashion.

As I understand it, schema-supporting functions would work on a PSVI.
If the extension functions were defined in terms of the PSVI, then the
schema language (or rather the schema syntax) that we used would be
independent. For example, we could come up with a simplified syntax
that used the same conceptual schema components as those used in XML
Schema, which would create a PSVI that holds the same information.

However, most of the other schema languages that are around at the
moment don't define a PSVI, indeed they purposefully keep away from
anything of the sort, for good reasons (like not wanting the meaning
of an XML document to change depending on whether a schema is
available or not).

So, given that the XML Schema PSVI is the only well-defined PSVI
around at the moment, then I think XPath extension functions should
use that for now. It might be possible to define mapping rules from
other schema languages onto this PSVI - use the names of the ref
elements in TREX to indicate some kind of type hierarchy, for example.

Of course I'm open to suggestions (though as we're starting to talk
about EXSLT extensions we should probably take it to list@exslt.org).



Jeni Tennison