[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: WD for Namespaces 1.1
From: "Bullard, Claude L (Len)" <clbullar@i...> > Namespaces are system flags to XML processors. > They don't belong in the core. Because names > of resources and names of locations of resources > in the system are conflated, you can't put them > in the core without tieing them directly to > the system. That violated platform independence. I don't see that this is any worse than using non-formal public identifiers in SGML: <!ENTITY xxx PUBLIC "http://www.topologi.com/" "http://www.topologi.com" > The point with XML is that it is not platform independent. It is designed for the WWW. If anyone needs archiving or platform independence for tricky jobs, they may still have to resort to full SGML. It is interesting to compare namespaces and the IS 8879 SGML idea of "Element Sets" (a group of declarations with only ELEMENT, ATTLIST and I think NOTATION). IMHO, Namespaces are just an extension of Element Sets (*not* architectures, Steve :-). Namespaces just make first-class what is a second-class structure (declaration groupings) in IS 8879 SGML. That there needs to be RDDL interposed between the namespace identifier and any actual schema is merely that we need to support plurality; one can imagine a RDDL server where referencing a namespace URI with a RDDL purpose as a parameter retrieves a schema directly. However the trouble with namespaces and DTDs is not so much that one has to use Michael McQueen's PE technique for prefixes, which is tiresome; rather it is because namespace were designed to allow modularity, and highly-closed content models such as supplied by DTDs (where ANY is the only way to get openness) restrict modularity to modules known at the time the schema was made. XML Schemas, RELAX NG and Examplotron are better in this regard, allowing various kinds of openness if you have the foresight to declare you element sets that way. Schematron is neutral w.r.t. openness/closeness: it starts being open but you add constraints; these constraints may themselves be open (such as "A should contain a B") or closed ( such as "A should contain only Bs"). Cheers Rick Jelliffe
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