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Re: Action needed: subClassOf on datatypes

From: pat hayes <phayes@ihmc.us>
Date: Tue, 2 Sep 2003 23:42:29 -0700
Message-Id: <p06001f01bb7b3bceda27@[192.168.1.2]>
To: Jan Grant <Jan.Grant@bristol.ac.uk>, Jeremy Carroll <jjc@hpl.hp.com>
Cc: w3c-rdfcore-wg@w3.org

>On Tue, 2 Sep 2003, Jeremy Carroll wrote:
>
>>
>>
>>  Summary:
>>  Prefer c++
>>  modify  the test case to say that the case is D-consistent with the
>>  empty graph, not that it is D-entailed by it;
>>  add D-inconsistent test using a different rdfs:subClassOf triple between
>>  xsd datatypes.
>>
>>
>>
>>
>>  pat hayes wrote:
>>
>>
>>  > (a) modify the test case doc by deleting the test case;
>>
>>  Not particularly OK, well unless the semantics doc discusses
>>  rdfs:subClassOf in datatyping clearly. i.e. this should not be left as an
>  > exercise for the reader.

Currently I have this text where the rule rdfD4 used to be:

"In addition, if it is known that the value space of the datatype 
denoted by ddd is a subset of that of the datatype denoted by eee, 
then it would be appropriate to assert that

ddd rdfs:subClassOf eee .

but this needs to be asserted explicitly; it does not follow from the 
subset relationship alone."


>  >
>>  > (b) modify the test case to say that this only follows under the
>>  > strengthened extensional semantic conditions on rdfs:subClassOf
>>  > described in section 4.1 of the semantics document;
>>
>>  not good
>>
>>  > (c) modify  the test case to say that the case is D-consistent with the
>>  > empty graph, not that it is D-entailed by it;
>>
>>  OK
>>  Also add a test case showing that
>>  xsd:string rdfs:subClassOf xsd:integer .
>>  is inconsistent.
>>
>>  > (d) modify the semantics of D-interpretations to insist that datatype
>>  > class subsetting *is* treated extensionally, so that the rule rdfD4 is
>>  > valid and the test case is OK. This can be done by adding the following
>>  > semantic condition on D-interpretations:
>>
>>  Prefer (c) to this.
>>  (Another option is to explicitly list rdfs:subClassOf relationships between
>>  xsd datatypes as true by fiat).
>
>This last option seemed the "obvious" one to me: that a datatype
>definition might well include subClassOf "axiomatic triples".

Well, if these are considered part of some external-to-RDF definition 
of some class of datatypes, then that is fine. I have no problem with 
that.

>
>The test case document currently doesn't have explicit
>"consistent/inconsistent" test cases; these have usually been encoded
>using entailment or non-entailment of false graphs.

Well, if y'all are happy to phrase things this way, then OK; but 
there is no such thing as a false graph, actually. About the best you 
could do to get a contradiction in RDF would be to have an XML 
literal clash, such as

ex:a ex:p "<NotALegalXMLString"^^rdf:XMLLiteral .
ex:p rdfs:range rdf:XMLLiteral .

>So the new test cases would be that:
>
>1.
>[[
>	xsd:integer rdfs:subClassOf xsd:decimal .
>]] DOES NOT rdfs+D(xsd:integer, xsd:decimal)-entail
>[[ FALSE ]] (the "false" graph)
>
>2.
>[[
>	xsd:integer rdfs:subClassOf xsd:string .
>]] rdfs+D(xsd:integer, xsd:string)-entails
>[[ FALSE ]]
>
>... is that ok?

Yes, modulo the above.

Pat


>
>
>
>
>
>--
>jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
>Tel +44(0)117 9287088 Fax +44 (0)117 9287112 http://ioctl.org/jan/
>It's a sad fact that the word "semantics" seems to have lost all meaning.


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Received on Wednesday, 3 September 2003 02:43:23 EDT

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