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RE: OWL Restrictions and RDF Named Graphs

From: Michael Schneider <schneid@fzi.de>
Date: Thu, 22 Apr 2010 09:25:37 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A001D52233@judith.fzi.de>
To: <nathan@webr3.org>
Cc: <public-owl-dev@w3.org>
Hi Nathan!

It is not clear to me what your actual question is and what you want to
achieve. But I can see several issues that I want to make you aware of. This
may help you to rephrase your question, or to reconsider your ideas.

1) Named graphs are not supported by OWL, neither semantically nor
syntactically.

2) The two restriction classes are equivalent to each other. I don't know
whether you have intended this. The two class expressions only differ in the
owl:onProperty part. But, as you state in your mail, the properties
sioc:member_of and sioc:has_member are inverse to each other, so the
property expressions "sioc:member_of" and "[ owl:inverseOf sioc:has_member
]" that occur in the owl:onProperty parts are equivalent to each other.
Hence both restriction classes are equivalent.

3) I don't know what you mean when you say that a certain class "equates to
asking" a named graph. I also don't know what you mean by "if [the class]
asserts [some statement]" (classes don't assert anything). But what I can
see is that the two given statements

  <http://ex.org/john#me> sioc:member_of <http://ex.org/groups#g1>

and

  <http://ex.org/groups#g1> sioc:has_member <http://ex.org/john#me>

are equivalent, since the properties sioc:member_of and sioc:has_member are
equivalent. So you cannot use these statements as selection criteria, since
if one statement is asserted/inferred (by whatever means), the other will be
asserted/inferred as well.
 
Michael

>-----Original Message-----
>From: public-owl-dev-request@w3.org [mailto:public-owl-dev-
>request@w3.org] On Behalf Of Nathan
>Sent: Wednesday, April 21, 2010 11:06 AM
>To: public-owl-dev@w3.org
>Subject: OWL Restrictions and RDF Named Graphs
>
>Hi All,
>
>Given two named graphs:
>
><http://ex.org/groups> {
>  <http://ex.org/groups#g1> sioc:has_member <http://ex.org/john#me> .
>}
>
><http://ex.org/john> {
>  <http://ex.org/john#me> sioc:member_of <http://ex.org/groups#g1> .
>}
>
>and given that:
>
> sioc:has_member owl:inverseOf sioc:member_of .
>
>then given the following 2 restrictions:
>
>  _:a owl:equivalentClass [
>	a owl:Restriction ;
>	owl:hasValue <http://ex.org/groups#g1> ;
>	owl:onProperty sioc:member_of
>  ] .
>
>  _:b owl:equivalentClass [
>	a owl:Restriction ;
>	owl:hasValue <http://ex.org/groups#g1> ;
>	owl:onProperty [ owl:inverseOf sioc:has_member ]
>  ] .
>
>
>and that we know <http://ex.org/john#me> at processing time (but not at
>owl creation time), and further that we need to be able to infer which
>of the two named graphs to ask, then would it be fair to say:
>
>the class _:a equates to asking the named graph <http://ex.org/john> if
>it asserts that
>  <http://ex.org/john#me> sioc:member_of <http://ex.org/groups#g1> .
>
>
>the class _:b equates to asking the named graph <http://ex.org/groups>
>if it asserts that
>  <http://ex.org/groups#g1> sioc:has_member <http://ex.org/john#me> .
>
>
>Thanks for any input,
>
>Nathan

--
Dipl.-Inform. Michael Schneider
Research Scientist, Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: michael.schneider@fzi.de
WWW  : http://www.fzi.de/michael.schneider
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Received on Thursday, 22 April 2010 07:26:45 GMT

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