W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > September 2003

Re: Action needed: subClassOf on datatypes

From: pat hayes <phayes@ihmc.us>
Date: Tue, 2 Sep 2003 23:42:29 -0700
Message-Id: <p06001f01bb7b3bceda27@[]>
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 

>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:
>	xsd:integer rdfs:subClassOf xsd:decimal .
>]] DOES NOT rdfs+D(xsd:integer, xsd:decimal)-entail
>[[ FALSE ]] (the "false" graph)
>	xsd:integer rdfs:subClassOf xsd:string .
>]] rdfs+D(xsd:integer, xsd:string)-entails
>[[ FALSE ]]
>... is that ok?

Yes, modulo the above.


>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.

IHMC	(850)434 8903 or (650)494 3973   home
40 South Alcaniz St.	(850)202 4416   office
Pensacola			(850)202 4440   fax
FL 32501			(850)291 0667    cell
phayes@ihmc.us       http://www.ihmc.us/users/phayes
Received on Wednesday, 3 September 2003 02:43:23 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 20:24:25 UTC