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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Character Entities: An XML Core WG View
 > Now that's an interesting problem, one that goes way beyond the nuisance > of DTD syntax leftovers in a schema-based world. This is the main problem of using entities, and it's the problem the Core WG failed to address at all. The problem with schemas and entities is not that schema doesn't give an entity definition mechanism (it can't given XML 1.0 well formed parsing rules) But rather that the whole thrust of W3C XML language design towards namespaces/schema/modularisation/etc is that rather than have monolithic document types in the SGML/DTD tradition one has smaller namespaced (possibly schema defined) language "modules" that you can plug together to create a language suitable for the job in hand. This works well enough for just mixing well formed documents and has possibilities of working for modules specified by schema. However as soon as any of these language modules suggests any character entities the whole "modularisation" scheme gets fundamentally crippled and you have to have a document wide set of definitions specified in DTD syntax that is consistent over all the modules. The fact it has to be in DTD syntax if nothing else is in that syntax is a minor annoyance, the fact that it has to be consistent is a major, near fatal, problem to the whole scheme. The Core WG document only addresses the "minor annoyance" and doesn't address any of the difficult issues. It seems to me that there are two possible ways to improve things. Either one could agree a common set of definitions across all the major vocabularies, so that in practice the problem doesn't arise even if the architecture doesn't really provide any support. As I've said earlier, I can't see this happening unless the W3C XML activity takes that on as a work item. Or one could experiment with ways to allow the definitions to be context dependent, which would allow mathml fragments to be stuck into docbook or xhtml without having the meaning of <mo>≈</mo> changing as you move from one host language to another. This requires either some major new entity mechanisms in XML 2 or (possibly preferably) a relaxing of the undefined entity error to a validity error so you could experiment with other mechanisms layered over a basic non validating XML parser. David _____________________________________________________________________ This message has been checked for all known viruses by Star Internet delivered through the MessageLabs Virus Scanning Service. For further information visit http://www.star.net.uk/stats.asp or alternatively call Star Internet for details on the Virus Scanning Service. 
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