Since XML Schema can also be used to define rules for XML instances
without a target Namespace I don't think it follows that XSD defines
rules for namespaces, it would be sort of silly to think that a schema
without a target namespace was defining the full allowable grammar of
the empty namespace.

Cheers,
Bryan Rasmussen


On Tue, May 13, 2008 at 10:34 AM, Michael Kay <mike@s...> wrote:
> > > An XML schema defines rules for a class of XML documents.
>  > >
>  > Under that definition, doesn't XSD fail?   It defines rules for a
>  > namespace not a class of documents.
>
>  Well, I wasn't intending it as a rigorous definition, but I think it's
>  defensible.
>
>  I don't know why you think XSD defines rules for a namespace. A (XSD) schema
>  defines rules for a set of named elements and attributes. In the concrete
>  syntax the rules are organized by namespace, but they aren't confined to a
>  single namespace.
>
>  It's true that XSD (intentionally) doesn't treat the document as the primary
>  unit of validation. But it still describes rules for a class of documents,
>  namely those rooted at one of the elements defined in the schema.
>
>  Anyway, I wasn't really talking about XSD or about any schema language in
>  particular. I was just arguing against the thesis that variety is good; in
>  my view it is a necessary evil caused by the inadequacies of the currently
>  available languages, starting with DTDs.
>
>  Michael Kay
>
>
>
>
>
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