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At 09:53 20/06/2006, Rick Jelliffe wrote: >There are indeed many useful kinds of schema languages that don't >have widespread currency yet. Many thanks Rick This is very useful - if nothing else it reassures me I am on a reasonable track. >In some of my company's products we use our own little schema >language that says > >* what elements are allowed or required >* what attributes are allowed or required >* what elements are only every found in first or last position Yes.. >We also have "usage schemas" which sample documents and generate all >the possible grandparent/parent/child paths in the document, and >checks other documents against these. > >Checking lists of tokens is indeed a very problematic area for >Schematron using the default XSLT 1 implementations. Agreed. >ISO DSDL was created to give a home and official status to these >kind of little languages. If anyone can come up with a technically >excellent and implemented little schema language that helps validate >some significant kinds of markup idioms that XSD or the other ISO >DSDL schema languages do not cover well (as is *entirely* possible), >I am certain the ISO SC34 WG1 group would be interested in >considering it for standardization. I am not a great fan of developing things through ISO - I have sat on ISO ctte and the speed is extremely slow. I am less concerned about post-acceptance. But I am actually hoping that there are others who are interested in doing this as well. >To be honest, I suspect that Schematron with a particular extension >could pretty much do what Peter requires. In particular, ISO >Schematron has a macro facility called abstract patterns that allow >you to be much more declarative in labelling the participants in a >schema relationship: you could have one like Good. This may be useful to pursue. If it is lightweight and useful I would be prepared to write my own implementation. ><sch:pattern name="required-child" abstract="true"> > <sch:rule context="$parent"> > <sch:assert test="$child">The parent should have a child</sch:assert> > </sch:rule> ></sch:pattern> $foo seems to be an argument of some sort > <sch:pattern name="eg" is-a="required-child"> > <sch:param name="parent" value="Angela"/> > <sch:param name="child" value="Suhai"/> > <sch:param name="position" value="1" /> > </sch:pattern> > >What this gives is enough markup that a custom processor can take >the schema and >generate code based on it. For example, to append a Suhai element >to the Angela >element in the first position. Yes >Abstract patterns represent, I hope, a significant advance in >home-made schema languages, because not only do you get the >background boring power of XPath validation, but you also get the >extra labelling required to enable identification of the parts of >constraints and assertion >tests. And that identification opens the door for re-targetting the >schema for purposes such as code generation or any kind of useful >purpose. XPaths are great because they are terse; abstract patterns >overcome the concomitant lack of declative expressiveness. Absolutely agreed. I think the main problem is simply enough courage to pursue this. P. >Cheers >Rick > > > > >Peter Murray-Rust >Unilever Centre for Molecular Sciences Informatics >University of Cambridge, >Lensfield Road, Cambridge CB2 1EW, UK >+44-1223-763069
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