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Re: Summary of the QName to URI Mapping Problem

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 15 Aug 2001 13:14:21 -0700
Message-Id: <v04210105b7a087dcda21@[130.107.66.237]>
To: Drew McDermott <drew.mcdermott@yale.edu>
Cc: www-rdf-logic@w3.org
>Thank you, Mr. Stickler, for a very clear discussion of the QName/URI
>problem.  I always blamed myself for not understanding how this was
>supposed to work, and it's nice to realize that no one else
>understands it either.
>
>The designers of XML clearly intended QNames to be the "skeleton" of a
>domain.  That is, if you were making up a notation for describing,
>say, luggage, you might want a predicate 'manufacturer', and it would
>end up as an element tag somewhere, in a context like
><lugg:manufacturer>...</lugg:manufacturer>
>
>The names aren't defined in any sense except that there is an API
>description somewhere that tells programmers how a compliant
>luggage-notation reader/writer is supposed to behave when it sees
>'manufacturer' in the International Luggage Language namespace.
>
>Then RDF introduced conventions such as that
>
><rdf:Description ...>
>    <rdf:type resource="{some URI}">
>    ...
></rdf:Description>
>
>may be abbreviated
>
><{some QName} ...>
>   ...
></{some QName}>
>
>where {some QName} and {some URI} must expand to the same resource.
>
>Example: We declare the namespace
>xmlns:foo="http://www.foo.org/names#",
>and then we can abbreviate
>
><rdf:Description ...>
>   <rdf:type resource="http://www.foo.org/names#wow">
>   ...
></rdf:Description>
>
>as
>
><foo:wow ...>
>   ...
></foo:wow>
>
>Obviously, QNames are playing a very different role here than in XML.
>No RDF processor is expected to know what 'foo:wow' means in the same
>sense that a program compliant with the International Luggage Language
>is expected to know what 'lugg:manufacturer' means.  Instead, QNames
>are being used as a URI abbreviation device.
>
>Does that mean I could write:
>
><rdf:Description ...>
>   <rdf:type resource="foo:wow">
>   ...
></rdf:Description>
>
>or
>
><"http://www.foo.org/names#wow" ...>
>   ...
></"http://www.foo.org/names#wow">
>
>The answer is a loud No! for the second, and, I believe, a somewhat
>softer No for the first.

Drew, could you say WHY you believe these to be the appropriate 
answers? I have to confess that I fail to see what the urgent problem 
is here. Suppose one were to answer "yes" to both: what exactly would 
break? (I'm sure there is an answer, but I still don't grock what it 
is.)

Pat

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Received on Wednesday, 15 August 2001 16:13:40 GMT

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