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RE: An idea I need help with, or told to stop wasting time on!

From: Michael Schneider <schneid@fzi.de>
Date: Mon, 7 Jun 2010 11:21:24 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A001E997BC@judith.fzi.de>
To: "Story Henry" <henry.story@bblfish.net>
Cc: <nathan@webr3.org>, "Linked Data community" <public-lod@w3.org>, <semantic-web@w3.org>
Hi Henry!

Story Henry wrote:

>If you look at the rdf semantics document it spends a lot of time
>showing how one can turn literals into bnodes. http://www.w3.org/TR/rdf-
>mt/
>
>(I can't quite remember where now)

This works for OWL (1/2) /Full/ as well. OWL Full uses the (unrestricted)
RDF abstract syntax as its native syntax; hence, "_:x owl:sameAs 'foo'" is
valid syntactically in OWL Full. And OWL (1/2) Full uses the OWL 1
RDF-Compatible Semantics [1a] or the OWL 2 RDF-Based Semantics [1b] as its
semantics, which is strictly layered on top of the RDF Semantics; hence,
"_:x owl:sameAs 'foo'" is semantically meaningful in OWL Full, meaning that
there exists a resource in the universe of discourse that happens to be the
string 'foo'. 

What I said was that it does not work in OWL /DL/. See Sec. 11.2 of the OWL
2 Structural Specification [2] for the syntactic "Restrictions on the Usage
of Anonymous Individuals" in OWL 2 DL ontologies, and see Sec. 2.2 of the
OWL 2 Direct Semantics [3] (the semantics of OWL 2 DL), which states that
the object domain (individuals, represented by URIs and bnodes) and the data
domain (data values, represented by literals) are disjoint.

>I wonder what the problem owl has with doing this. And also I wonder if
>it is easy to create some new owl version that could deal with that.

No such need. This language exists and has always been around: it is OWL
(1/2) Full. Although, I'm starting to get the bad feeling that many people
seem to miss the point what the purpose of this language is. The whole idea
behind OWL Full is having a fully RDF compatible variant of OWL, which
provides semantic expressivity comparable (but not necessarily perfectly
equal) to OWL DL. Technically (as you have read the RDF Semantics spec, the
following should be familiar terms to you), OWL 2 Full (actually, its
semantics, the RDF-Based Semantics) is a "semantic extension" of RDFS (or
D-entailment, to be more precise), providing "vocabulary entailment" for all
the URIs of the OWL (2) vocabulary. You may want to read Chap. 1
("Introduction") of [1b] for further explanation (and, again, you will find
a lot of familiar sounding terms and concepts there).

Michael
 
[1a] http://www.w3.org/TR/owl-semantics/rdfs.html
[1b] http://www.w3.org/TR/2009/REC-owl2-rdf-based-semantics-20091027/
[2] http://www.w3.org/TR/2009/REC-owl2-syntax-20091027/
[3] http://www.w3.org/TR/2009/REC-owl2-direct-semantics-20091027/

--
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 Monday, 7 June 2010 09:22:10 UTC

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