what is "completely different" [Re: RDF, Namespaces, and Versioning?]

james anderson James.Anderson at mecomnet.de
Wed Feb 10 19:21:30 GMT 1999

What is the concensus (?!) here on how one should interpret "completely
different" in the passage below?

David Megginson wrote:
> In other words, ... I cannot use
> "{http://www.megginson.com/ns}result" in two different specs for two
> completely different purposes.

I understand that the intended reference was to declarations in two different
documents. Although not noted in the original note, the case of conflicting
use within a single document is clear without discussion. Which means that
"two different specs" could well be a resource with the same URI which is
included into two distinct documents.

If the name is an element name, would all definition instances be required to
have identical content models? Or maybe "equivalent" models? (For example,
under equivalence classes ANY / EMPTY / element content / pc content / mixed
content.) Equivalent models for all constituents which are in the same
namespace as the element name? Equivalent models for all constituents which
appear in namespaces declared in some "canonical" DTD?

If the name is an attribute name, would all definitions be required to be
identical? All definitions for elements with identical names? Or maybe all
definitions must specify the same attribute type? Or class of attribute type
(whereby all enumerated types are "equivalent")?

The question is, how much is an application permitted to cache? If it has seen
all the names before, does it need to fetch the "definitions" again, or can it
reuse the ones it has?
Is the answer to this question different for attribute and element
declarations that it is for entities? Maybe there is a distinction to be made
between structural and non-structural entities?

My experience with sgml is limited to reading, but it indicates that such
expectations would be disappointed in that world.

Will the presence of universal names perhaps permit different expectations for
distributed compound XML documents?


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