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RE: ISSUE-3 and RDF simple entailment

From: Michael Schneider <schneid@fzi.de>
Date: Fri, 29 Feb 2008 14:54:57 +0100
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A07513E4@judith.fzi.de>
To: "Jeremy Carroll" <jjc@hpl.hp.com>
Cc: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>, "Booth, David (HP Software - Boston)" <dbooth@hp.com>
Hi Jeremy! Hello David!

Jeremy Carroll wrote on Friday, February 29, 2008:

>One question that came up in HP discussion was whether the proposed 
>resolution to ISSUE-3 would break the monotonicity requirement for 
>semantic extensions
>http://www.w3.org/TR/rdf-mt/#MonSemExt
>
>I suggested that the proposal does break this requirement. 

AFAICT, this topic is only relevant for languages which claim to be
"semantic extentions" as defined by [10]. In this way, RDF semantics is a
semantic extention to Simple Entailment, RDFS to RDF, and both OWL-1.0-Full
and pD* are semantic extentions to RDFS. This is the "layered" approach
which I described in [20]. In fact, the "delta to OWL-1.0-Full idea", which
we discussed in an earlier telco, would mean that OWL-1.1-Full is becoming a
semantic extention to OWL-1.0-Full. 

But neither OWL-1.0-DL nor OWL-1.1-DL claim to be such a kind of semantic
extention to RDFS. So you cannot reasonably apply the "General monotonicity
lemma" from the RDF(S) semantics spec to them, where you have to "Suppose
that Y indicates a semantic extension of X".

>Here are the 
>test cases, are these correct?
>
>Here is a simple test case:
>
>A:
>_:a rdf:type owl:Thing.
>eg:dp rdf:type owl:DatatypeProperty .
>_:a eg:dp "foo".
>
>B:
>_:b rdf:type owl:Thing.
>eg:dp rdf:type owl:DatatypeProperty .
>_:b eg:dp "foo".
>
>A simple-entails B.
>A simple-entails A.

Yes to both.

>A owl-1.0-dl-entails B.
>A owl-1.0-dl-entails A.

Not quite sure about this, but I believe to remember Peter saying so in some
telco. (I also remember that I was surprised about his answer at that time.)

>A does not owl-1.1-dl-entail A.
>A does not owl-1.1-dl-entail B.

If bNodes will be interpreted as skolems in 1.1-DL, then yes, these will be
non-entailments.

>If I have understood some of the other aspects of OWL 1.1 DL then also
>the following:
>C:
>_:c eg:dp "foo".
>
>D:
>_:d eg:dp "foo".
>
>C simple-entails C.
>C simple-entails D.
>C does not owl-1.1-dl-entail C.
>C does not owl-1.1-dl-entail D.
>
>
>Note: these show why this change while in keeping with Peter's 
>characterization [1] of the relationship between OWL Full and OWL DL 
>(OWL DL is weaker than OWL Full), misses the relationship 
>between OWL DL 
>and RDFS, which is - on the syntactic subset that is OWL DL, OWL DL is 
>stronger than RDFS.

This may or may not be the case. Anyway, I would be very reluctant to make
this "observed" property a requirement for the DL flavours of OWL, now or in
the future. It has been the basic difference between OWL-1.0-DL and
OWL-1.0-Full that DL is semantically based on some specific description
logic (SHOIN(D) in the case of 1.0-DL), while Full is intended to be a
semantic extention to RDFS. These are two very different design principles,
so I wouldn't even easily come to the idea that OWL-x.y-DL might be
semantically a stronger language than RDFS. 

Under this pov, even the other direction, that OWL-Full is demanded to be
semantically a stronger language than OWL-DL, might become questionable. But
in this case, this property seems at least to be easier to obtain, since
these two languages share the same OWL specific language features, while
OWL-Full additionally consists of all the semantic properties inhereted from
RDFS. So this request looks quite reasonable to me.

Bottom line: I *won't* demand OWL-1.1-DL to be a semantical upper language
to RDFS, but I *will* ask for OWL-1.1-Full being a semantical upper language
to OWL-1.1-DL.

Cheers,
Michael

[10] <http://www.w3.org/TR/2003/WD-rdf-mt-20030123/#DefSemanticExtension>
[20] <http://lists.w3.org/Archives/Public/public-owl-wg/2008Feb/0068.html>

--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
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Fax  : +49-721-9654-727
Email: Michael.Schneider@fzi.de
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Received on Friday, 29 February 2008 13:55:23 GMT

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