[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Victory has been declared in the schema wars ...
On Nov 28, 2006, at 14:21, David Carlisle wrote: > Of course this rng based xhtml2 hasn't proved to be overwhelmingly, > popular, before declaring victory we'd better keep an eye on html5 > which > manages to do without dtd or xsd or rng, or any other recognised > schema > language at all..... I think not having a normative schema for HTML5 is a very good idea. None of the current schema languages (not even Schematron) are adequate for expressing all the conformance requirements of HTML5. Experience has shown that people become too schema-focused if there is a normative schema: DTDs aren't adequate for expressing the conformance requirements of HTML 4.01, but still people behave as though they had checked for conformance when they have validated against a DTD. Still, HTML5 can be counted as a bullet point in favor of the RELAX NG camp. The only schema for HTML5 in the works is a RELAX NG (Compact Syntax) schema with companion Schematron assertions ( http:// syntax.whattf.org/ ). A conformance checker for HTML5 requires non- schema checking code to fill the gaps that RELAX NG and Schematron can't fill (conveniently or at all). For example, http:// hsivonen.iki.fi/validator/html5/ checks for table cell overlap in Java code--not in RNG, XSD or Schematron. But back to RNG vs. XSD: Dare Obasanjo pointed out an important issue on his blog at http://www.25hoursaday.com/weblog/PermaLink.aspx? guid=19adeb36-16d9-4cb6-a99f-cf3d1b15de5c Validation and data binding are different problems. RELAX NG is great for validation. For this purpose, allowing ambiguous grammars and making datatypes just check whether a string belongs in a formal language are great features. Trying to introduce something as innocent-looking as the RNG DTD compat features already becomes an annoyance that gets in the way of writing nice ambiguous schemas. Infoset augmentation as a side effect of validation is not cool. A lot of people use XSD for data binding. RNG doesn't do data binding *by design*, so telling those people to use RNG for data binding doesn't seem to help. Personally, though, I have serious doubts about whether automated data binding is a good idea--in particular due to service versioning concerns. And I am not suggesting that XSD is a good solution for data binding, either. P.S. Readers of this thread may be interested in an online RNG and Schematron 1.5 validator: http://hsivonen.iki.fi/validator/ -- Henri Sivonen hsivonen@i... http://hsivonen.iki.fi/
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