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From: "Murali Mani" <mani@C...> > I also *fully* agree that RELAX NG is the most important thing that is > happening at present. But the point is that it is _still_ happening: the different flavours of RELAX were not good enough for James' criteria so he made TREX; TREX is not good enough for Murata-san so they are co-operating on developing it further, over at OASIS. If James, one of the keenest technocrats around, is still working on a language after more than a decade experience with DTDs, with reviewing the efforts of the XML Schemas WG, and after consideration of the seminal DSD and RELAX, what does that suggest? It suggests to me that _any_ standard for schemas must be considered either premature or interim, at the current time. And this is exactly the approach that the XML Schema WG has taken: XML Schemas 1.0 is provisional both in small matters (because of the work of XML Schemas 1.1) and in larger matters (the mooted XML Schemas 2.0). Murali carpets W3C XML Schemas as bad, but he is in fact only interested in one area of them. The areas of datatyping, schema construction, keyrefs, name handling have all been pretty well received: even though they are all amenable improvement (respectively localizable datatypes, modules, better keyrefs, status of schemaLocation). (These are things I hope XML Schemas 1.1 will improve.) The areas that have not been well received are -- perceived complexity of the spec (though complexity of the spec and complexity of the technology are not at all the same thing: looking at the two diagrams in the specs shows there is not spaghetti at the top-levels) -- type derivation (is it very useful for non-databases?) -- the details of the grammar (is it overly restictive/under-powered/unreasonable) I don't see RELAX NG as a competitor to XML Schemas; to the contrary, I think we can only ascend to XML Schemas 2.0 when there are credible alternative languages developed and deployed, by which we can judge XML Schemas 1.n. (It is dialectic development.) So RELAX NG is the best friend of the XML Schema WG, in the long run: it is their unofficial research lab. I don't know if Murata-san works on company time on RELAX-NG, but I were his manager at IBM I would allot him spend as much time as possible on it, because of IBM's commitment to XML Schema. If he is working on company time, then IBM should be congratulated. RELAX NG may be just as important for XML Schemas 2.0 as the XML Schemas 1.1 standards work. But I hope deployment experience from XML Schemas 1.n will be much more influential than any speculative analysis: I think speculative analysis is the methodology used both in XML Schemas and RELAX NG and ultimately it provides no guarantee of producing a productive result. When a spec is made by committees sitting around the globe making up user requirements on the spot as needed to justify their technological and aesthetic predelictions, with no regard for how humans think and act, the emperor has no clothes, no matter how relaxing he may find it. An alternative take on all this would be that, if grammars (one of the most exhaustively studied abstractions) introduce problems (such as the problem with adding or substracting schemas from each other) that are still (after 16+ years of schema language development) then perhaps they are dense and compelling distractions which are actively preventing us from adopting more straightforward schema paradigms. Cheers Rick Jelliffe
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