Re: XML Encoding of XPath: Examples

[Rick Jelliffe <ricko@allette.com.au>]

From: Eric van der Vlist <vdv@dyomedea.com>

> I agree that the correspondence is probably one way (a pattern may be
> written as a rule but a rule cannot always be written as a pattern).

My point is slightly different. Two very different schema languages may have
schemas that accept the same files without complaint: but that is only one
aspect of a schema language and it may not even be the most important one.

A schema language builds some kind of data model concerning the data: in the
case of XML Schemas this data model is that there are complex and simple
types and that types get derived from types and information items may belong
to a type.

In Schematron the data model is that there are patterns which are objects
that exist independently of particular elements, and that patterns may
connect to parts of a document as a series of subject elements with
particular roles.  A pattern does not adhere to its context node in a
particular way: the context node is just the most convenient node to pivot
the pattern around.

Cheers
Rick Jelliffe