Re: Question about Extensional Entailment Rules

Jan Grant wrote:
>On 2004年8月26日, Nick Bassiliades wrote:
>
> 
>
>>Hi all,
>>
>>I would like to ask you whether I am missing something from the extensional
>>entailment rules ext1&2
>>in the RDF Semantics document (http://www.w3.org/TR/rdf-mt/).
>>
>>Rule ext1 says that when:
>> uuu rdfs:domain vvv .
>>and
>> vvv rdfs:subClassOf zzz .
>>are true, then the triple:
>> uuu rdfs:domain zzz .
>>should be added.
>>
>>However, IMHO this looks rather bizarre! This rule states that when a property
>>has a certain class as a
>>domain, it must also have all its superclasses as a domain. I believe that
>>it's the other way around:
>>all the subclasses of a class can be domains for the property uuu.
>>
>>For example,
>> uni:faculty rdfs:subClassOf uni:staff . (/Faculty members are member of
>>the staff/)
>> uni:teaches rdfs:domain uni:faculty . (/Faculty members teach/)
>>then we infer with rule ext1 that:
>> uni:teaches rdfs:domain uni:staff . (/All members of the staff can
>>teach!/)
>>
>>I would expect it to work the other way around:
>> uni:lecturer rdfs:subClassOf uni:faculty . (/Lecturers are //Faculty
>>members/)
>> uni:teaches rdfs:domain uni:faculty . (/Faculty members teach/)
>>then we infer that:
>> uni:teaches rdfs:domain uni:lecturer . (/Lecturers // can teach/)
>>
>>Am I missing something here?
>> 
>>
>
>The semantics are conjunctive. To say that "the domain of uni:teaches is 
>uni:faculty" means, if you have statements of the kind
>	X uni:teaches Y .
>then X must be a member of uni:faculty: we can infer that about its 
>type. What we can't do is infer that X is a uni:lecturer; but we _can_ 
>logically infer that X must also be a member of uni:staff. The rules for 
>domain and range are universally quantified in this fashion, so whilst 
>it looks odd it's right.
>
> 
>
However, the above scenario is already covered by existing entailment rules:
IF
 1) X uni:teaches Y . &
 2) uni:teaches rdfs:domain uni:faculty . &
 3) uni:faculty rdfs:subClassOf uni:staff .
THEN
 4) X rdf:type uni:faculty . (due to (1) & (2) and rule rdfs2)
&
 5) X rdf:type uni:staff . (due to (4) & (3) and rule rdfs9)
I am not sure why rule ext1 is necessary, since it is subsumed by the 
two other rules.
Nick
 
-- 
*********************************************************************
* Dr. Nick Bassiliades, Assistant Professor *
* Dept. of Informatics, Aristotle University of Thessaloniki *
* 54124 Thessaloniki, Greece *
* *
* Tel: +302310997913 E-mail: nbassili@csd.auth.gr *
* Fax: +302310998419 URL: http://lpis.csd.auth.gr/people/nbassili *
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