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RE: Digest URI's

From: McBride, Brian <bwm@hplb.hpl.hp.com>
Date: Mon, 10 Apr 2000 13:20:02 +0100
Message-ID: <7686E88F1253D311A867006008CD059F113748@0-mail-1.hpl.hp.com>
To: "'www-rdf-interest@w3.org'" <www-rdf-interest@w3.org>
>
>You can make RDF statements about a model.
>

Yup - statements about a model value.

>If a GUI app is used to create the model,
>well, it already has some URIs for all resources.

I'm not sure thats true.  What is the basis for this assertion?  An
application (it need not be a GUI) could certainly make one up, but I'm not
sure how useful it is to do so.

>
>This is exactly my understanding of the role of anonymous resources. As
>mentioned, I believe anonymous resources don't belong to the model.
>

Is this belief based on the current spec (which part?), or would you propose
to modify/clarify the spec?

>> Would the proposed algorithm assign the same digest URI to 
>both the authors
>> (they are a husband and wife team) in the following fragment 
>of serialised
>> RDF?
>> 
>> <?xml version="1.0"?>
>> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>>          xmlns:DC="http://purl.org/dc/elements/1.0/">
>> 
>> <rdf:Description about="http://homepage/SmithFamily">
>>   <author>
>>      <rdf:Description>
>>         <surname>Smith</surname>
>>      </rdf:Description>
>>   </author>
>>   <author>
>>      <rdf:Description>
>>         <surname>Smith</surname>
>>      </rdf:Description>
>>   </author>
>> </rdf:Description>
>> </rdf:RDF>
>
>Yes. There is no way to distinguish between these two 
>resources based on
>the context (remember, the digest algorithm should to be
>order-independent, therefore XML ordering does not count).
>
>However, even a human (at least me ;) would have difficulties
>disambiguating the above RDF description: did the author 
>really mean two
>different entities, or was it just a cut-and-paste typo?
>


What you say is true.  I am the author, I guess, and yes I did mean to write
a model that stated there are two authors with a common surname. It is not a
cut-and-paste typo. I believe this is legal RDF.

However, the proposed digest algorithm would assign the same URI to both
authors.  Given that the formal spec for the RDF model is defined in terms
of sets (i.e. duplicates disappear), the model that would then result from
the above RDF fragment, given the proposed digest URI algorithm would be:

	<author, "http://homepage/SmithFamily", [digest-uri]>
	<surname, [digest-uri], "Smith">

The model should be:

	<author, "http://homepage/SmithFamily", #anon1>
	<surname, #anon1, "Smith">
	<author, "http://homepage/SmithFamily", #anon2>
	<surname, #anon2, "Smith">

And this indeed is the result produced by the SiRPAC based demo at
http://jigsaw.w3.org:8000/description.


The RDF that was input described a model with two authors that were
indistinguishable.  That is not the same as a model with only one author.
Because the parser does not have enough information to distinguish between
two resources, should it assert that they are the same resource?

Brian McBride
HPLabs
Received on Monday, 10 April 2000 08:20:52 GMT

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