Re: Schema Namespace name, schemaLocation,and Schema V ersio
[Rick Jelliffe] From: "David Carlisle" <davidc@n...> > Take a look at the namespace spec. > Namespaces are not about semantics they are about names. Well, they really are about modularity which cannot really get too far from ideas of semantics. [Tom P] From a strict point of view, the modularity is on a syntactical level, though, not a semantic level. If I specify an ex:address element rather than an xy:address element, I am specifying the __structure__ of the address element and its children. This lets me know how to process its structure. It is inviting to assume that any semantics that originally attached to the ex:address element should come along with my use of it, but the Recs say nothing about that. Since neither XML Schema, DTDs, nor RELAX NG specify semantics, there is no standard mechanized way to specify or control the semantics of a document design. Suppose that we import an ex:person element and it has an attribute "id". The original schema had an annotation saying that the id is intended to be a (US) social security number. But after we have started to use our schema, we decide to that it needs to allow either an SS number or the person's driver license number (in many US states you can use state-assigned number in place of your SS number for a driver's license). Should we stop using ex:person? This is a semantic issue, not a structural or syntactical one (and gets into Len's pet area of contracts). Suppose that we decide to continue to use the id attribute even though its meaning has changed a bit. The syntactic consequence is that ex:person will still work fine with my software. If we decide that we should have another attribute, called "newid", that would be a semantic decision and we could work out the syntactical consequences (perhaps an extension of ex:person if it can be extended). Of course, we may consider the syntactic consequences as we decide whether the semantic issues are strong enough to warrant a change in the structures. Those practical tradeoffs are where the lines get blurred. But I think it is useful to start from a strict position - syntax is syntax, not semantics - and only deviate for good reasons. The Recs - XML, Namespaces, Schema - only deal with syntax. The semantic issues are an overlay. Cheers, Tom P
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