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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Vocabulary Combination
 "Rick Jelliffe" <ricko@a...> wrote: | From: "Arjun Ray" <aray@n...> |> Right. Namespaces are neither necessary nor sufficient for the general |> problem of vocabulary combination. | | I think this is where the new generation schemas languages fit in. They could, but I wouldn't be so quick to th conclusion that schema languages are needed here. | The namespaces set general semantics, I don't think this is true. I would attach the notion of semantics to "vocabulary" (in the sense that it's been bandied about in discussions of this sort - see the Namespaces Rec too!) rather than to "namespace" (in the sense of the Rec). The fact that a bunch of universal names share a URI "prefix" is no more than a coincidence. They need not be parts of any coherent schema at all. They're just a smorgasbord. Conversely, the notion of "vocabulary" does carry an implication of an underlying schema - that there are definite ways to organize the names when applied to a document. If it's meaningful to say that a document could have only a single vocabulary, then the possibility of multiple vocabularies raises the issue of knowing (or determining) to which parts of the document each of these would apply. Which in turn would suggest the legitimacy of the notion of a vocabulary-specific "view", i.e. the part of the document which is *coherent* with respect to a particular vocabulary. (Contrast this with random collections of allegedly universal names - there is no necessary notion that they contribute to a coherent whole in terms of their *own* "namespace".) | the schemas tell you how they must be combined. But this is not necessarily an issue of schema combination. There's a difference between whether schemas are mergeable and whether they are miscible - for the particular document instance only. That is, the use of multiple vocabularies could have been a one-off - there was no intent to synthesize a new schema (as a repeatedly instantiable document type). IOW, it should be possible for a document, as an instance by itself, to claim conformance to different schemas in its various parts, without being obliged to assert that there is some unitary schema for the entire document unifying these various schemas. But that's still jumping the gun. The minimum necessary is a means for a document to assert what parts of it are "assigned" (by authorial intent) to a vocabulary specific view, such that if anyone cared they could run a validator on that view to see if it comformed to the corresponding schema. (We *know* that's a separate issue: this discussion is about parsing, not validation.) | What neither of them necessarily set is the semantics of combination (i.e. | what do these information items mean together, what do they mean apart) | The best that a schema can do is constraint a document language to only | accept documents that has certain semantics-of-combination. Yes, but before one checks against a schema, one must know what part of the document to submit to the check. I don't see why every schema must apply to all of the document, or why a document should have a unitary schema when all the author intends is conformance of various parts only. 
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