Yet another validity question

[John Cowan]

roddey at us.ibm.com scripsit:

> I just now, for whatever reason, got around to noticing that the James
> Clark 'valid' tests imply that you can reference an element in a content
> model without its ever having been declared, for instance:

[snippage]

> What am I missing here?

Extensibility.

By allowing unknown element types in content models, we allow
documents to define such element types according to their needs,
using either the internal subset or a containing external DTD,
and then they will "just work" as content of the existing elements.

-- 
John Cowan					cowan at ccil.org
		e'osai ko sarji la lojban.

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