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From: "Bullard, Claude L (Len)" <clbullar@i...> > 2. Learn RELAX NG and XML Schemas. Schematron has no official > standing, but without it, the weaknesses of RNG and XSD aren't > easy to overcome. Databases typically need the ability to > specify co-occurrence constraints (if this value, then that > value). So one needs it. Schematron is currently being standardized as part of ISO DSDL. I hope it will be an ISO standard by the end of this year, if everything goes smoothly. I hope to fold in some of the ideas from the similar XCSL, whose author I met in Barcelona last week, in particular the <let> element which allows variables to a certain extent: this will simplify dissecting strings into parts and treating their parts as numbers (e.g. dates, etc) with interrelationships. At the moment this is possible but cumbersome. There are no backward-incompatible changes with Schematron 1.5 planned. We are definitely targeting ISO Schematron as a convenient way to express constraints that are difficult or confusing in other schema languages: express simple relationships in other languages with simple content models, and leave the complex constraints to Schematron schemas. Cheers Rick Jelliffe
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