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Some further questions: say I have to design a schema of some type and associate it to other schemas based on it. In other words, I would have a schema of abstractions that the secondary schema would make more substantial by derivation. 1. Is RNG up to that? How? 2. Would the AF NG be a way to get that done? I've drafted such a thing using XML Schema for the HumanML project. We are about to finalize requirements and have picked XML Schema as well as RDF. But you are right that XML Schema is not easy and I have a queasy feeling that our target user groups for HumanML will have a hard time working with it. Should we reconsider and if so, should we simply include RELAX NG along with XML Schema, or perhaps use it? Again, my concern here is that we will already have a hard design to master (use of base schema). Whatever lightens that load and encourages use of the base is of value. len From: John Cowan [mailto:jcowan@r...] "Bullard, Claude L (Len)" scripsit: > 1. More productive. Can one compose faster, is it easier to learn, > does is do what I need to do in the framework? Well, I'm a fairly bright sort of guy, and I could run RNG into my rapidly aging brain with no trouble, but XSD (part 1) is still defeating me. I would say that RNG is far and away the least restrictive schema language of its type (excluding Schematron, Examplotron, Hook, etc.). In essence, if you can write down RNG, and it makes any sense at all (no elements within attributes or consecutive datatypes, e.g.) then it just *works*, period. It has three syntaxes: XML-instance, programming-language, and DTD, for validators, schema authors, and legacy respectively. Its main weakness as against XSD is that it has no key/keyref support other that DTD-compatible ID, IDREF, and IDREFS (which are technically an extension, but supported in the existing validators). These were present in earlier drafts, but were too messy and hard to get right in the general case, and were dropped from RNG 1.0. Identity constraints are really orthogonal to structural ones in any case. This is a job waiting for someone to have a brain-wave. The spirit of RNG is closely related to that of DTDs: there is a smooth mental upgrade path. As a result, the DTD-RNG conversion tool is a masterpiece of structure preservation: it does its very best to make whatever structuring in the way of parameter entities that the DTD has, appear transparently in the RNG as well.
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