Graham Hannington wrote:
Argh... I've just found out that one of the XML document
types that I'd
planned to document (by writing an XDR schema, and then using XSLT to
produce documentation in XHTML) cannot be fully expressed in
either XDR or
XSD, but (from what I've read in Jeni Tennison's tutorials)
*might* be able
to be described via Schematron.
This is because, in this XML document type, allowable child
elements vary,
depending on the value of an attribute in the parent element.
This can certainly be described easily in Schematron.
NB Schematron is very expressive: a Schematron schema consists of a bunch of
pattern-matching rules (which are xpath expressions), and associated textual
descriptions and diagnostic messages.
This is very like an XSLT stylesheet, and in fact Schematron schemas ARE
typically applied by transforming them into an XSLT stylesheet, and then
using that XSLT to transform an instance document, producing a "report"
document describing the validity of the instance doc. So Schematron is a
very appropriate application for XSLT - maybe we're not TOO off-topic yet
;-)
For example: a schematron schema for the example you gave would be something
like:
<sch:schema xmlns:sch="http://www.ascc.net/xml/schematron"; >
<sch:pattern name="check 'element' element">
<sch:rule context="element[(_at_)attrA='this']">
<sch:assert test="*[not(self::elementX1) and
not(self:elementX2)]">
element with attrA = "this" may only contain elementX1 or
elementX2
</sch:assert>
</sch:rule>
<sch:rule context="element[(_at_)attrA='that']">
<sch:assert test="*[not(self::elementX3) and
not(self:elementX4)]">
element with attrA = "that" may only contain elementX3 or
elementX4
</sch:assert>
</sch:rule>
</sch:pattern>
</sch:schema>
You can see the "rule-based" schema is already almost in the format you want
(unlike a DTD or XMLSchema) and the transformation to HTML is very
straightforward - I suggest you bite the bullet and write one to suit
yourself.
http://directory.google.com/Top/Computers/Data_Formats/Markup_Languages/XML/
Validation/Schematron
Cheers!
Con
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