From: "Eddie Robertsson" <erobertsson@[...].au> 

>  Len, I'm a huge fan of Schematron but I sometimes find that defining
>  structure in Schematron can be a bit complex and cumbersome.  

Probably the main infelicity in Schematron is that when attempting
to dissect datatypes into parts, the XPath gets unworkably long.

At the Barcelona conference there was a very nice paper on
a Portuguese language called XML Constraint Specification
Language which is along the same lines as Schematron.  
Schematron 1.5 is better than it for higher-level
facilities (multiple assertions, rule chaining, diagnostics, phases)
but XCSL has a <let>  statement which makes variables
available and so tames those long datatype dissections.

For ISO Schematron, I hope to incorporate XCSL's <let> 
statement into Schematron rules.  That will greatly increase
Schematron's friendliness for delving into structured text 
values.

Cheers
Rick Jelliffe

P.S. Schematron is now available as a PHP module.
See http://www.ascc.net/xml/resource/schematron/schematron.html

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