I wrote:

...

"Note that DTD-based validation is not namespace-aware in the following sense: a DTD constrains the elements and attributes that may appear in a document by their uninterpreted names, not by (namespace name, local name) pairs."

So in the DTD, the prefix *is* semantically significant. And Clark notation is irrelevant, because there is no use for the URI in the DTD.

John Millikin wrote:

If I'm reading that paragraph correctly, the prefix is not significant, or even present, in a DTD. You only use the local name.

No, the spec is quite clear about that. Element names and attribute names are "qualified names", but their namespaces are not "interpreted"; those terms are defined precisely earlier in the spec. In order for that to produce XML documents that make sense, the spec recommends that you use #FIXED for the xmlns:foo attribute in the appropriate places in the DTD. Thanks, Yitz