Re: Who can implement W3C XML Schema ?
From: "Jonathan Robie" <jonathan.robie@s...> > Does anybody have real data on the market penetration of XML Schema? I > think that vendor support for XML Schema is clear, but if Adam is right, > that's irrelevant. Vendors seem to believe that people are actually using > XML Schema, too. Are they right? Do we have real evidence on this question? Which market? Could we guess Publishing market: almost 0% uptake Interprocess-communications-using market: medium uptake DBMS-to-middleware market: high uptake because XML Schemas is little value for publishing (because people need entities, therefore they cannot throw the DTDs away, therefore XML Schemas being so monolothic creates a duplication of effort for not much reward. However, people who expect data definitions and database-style datatyping and so-called schema management tools will find XML Schemas more congenial. Most people who slag off XML Schemas do so because one size cannot fit all. The initial step has to be figuring out which schema language or processing combination is appropriate for each sector. I expect that as publishing-messaging XML bifurcates from database-XML that it will settle down to DSDL (e.g. RELAX NG + Schematron + localizable datatypes) for the former and XML Schemas (+ SAF and embedded Schematron) for the latter. XML Schemas should have been modular: it was not because of the decision that every XML Schema processor should return the same ultimate valid/invalid distinction on a document. This logically forbids subsets, which is great promotor of modularity. The irony is that this lack of modularity probably has resulted in the opposite result: XML Schemas implementations are so poor in agreement. I think it would be really useful for the XML Schema WG to, rather than rewrite part 1, split parts 1 and 2 into six or eight parts: 1) Schema construction and namespace handling 2) Type derivation and labelling 3) Structures 4) Keys and uniqueness 5) Primitive datatypes and facets 6) Datatype derivation and built-in derived types 7) Schema Adjuct Framework 8) Embedded Schematron Schemas which would allow greater modularity, let readers and implementers concentrate and advertise conformance on different parts, and fit in with ISO DSDL, for users who, say, want to use RELAX NG with XML Schemas primitive datatypes. The verbal difficulty of the spec is one thing; but the difficulty of each paragraph is multiplied by the lack of modularity in the subject of the spec. Cheers Rick Jelliffe
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