RE: ISSUE-3: REPORTED: Lack of anonymous individuals

Hi,

Indeed if you use triples syntax or FOL syntax (as you did initially) or any
other syntax that allows you to play with variable, then you can construct
these things/problems. But I was asking about using OWL abstract syntax.

Greetings,
-gstoil

> -----Original Message-----
> From: Boris Motik [mailto:boris.motik@comlab.ox.ac.uk]
> Sent: Friday, November 09, 2007 12:50 PM
> To: 'Giorgos Stoilos'
> Cc: public-owl-wg@w3.org
> Subject: RE: ISSUE-3: REPORTED: Lack of anonymous individuals
> 
> Hello,
> 
> You can use bnodes in RDF data arbitrarily. Take a look at
> 
> http://www.w3.org/TR/rdf-primer/#structuredproperties
> 
> There, you'll see triples containing identifies form _:xxx; all of these
> are bnodes. Each such identifier is taken to represent one
> existentially quantified variables.
> 
> 
> 
> The bnodes in RDF are the same as labelled nulls in databases. Database
> people have studied in depth what kind of semantics is
> appropriate for null values. A really good paper on this topic is the
> following:
> 
> Tomasz Imielinski, Witold Lipski Jr.: Incomplete Information in Relational
> Databases. J. ACM 31(4): 761-791 (1984)
> 
> The practical consequences, however, are rather severe: answering queries
> with labelled nulls is NP-complete. This is one of the
> main reasons why practical database systems don't implement labelled
> nulls. (Another reason is that your answers are not so much
> better even if you use labelled nulls.)
> 
> Boris
> 
> 
> > -----Original Message-----
> > From: Giorgos Stoilos [mailto:gstoil@image.ece.ntua.gr]
> > Sent: 09 November 2007 10:18
> > To: 'Boris Motik'
> > Cc: public-owl-wg@w3.org
> > Subject: RE: ISSUE-3: REPORTED: Lack of anonymous individuals
> >
> >
> >
> > > -----Original Message-----
> > > From: Boris Motik [mailto:boris.motik@comlab.ox.ac.uk]
> > > Sent: Thursday, November 08, 2007 2:14 PM
> > > To: gstoil@image.ece.ntua.gr; public-owl-wg@w3.org; 'Carsten Lutz'
> > > Subject: RE: ISSUE-3: REPORTED: Lack of anonymous individuals
> > >
> > > Hello,
> > >
> > > Here is an explanation how anonymous individuals in ABoxes correspond
> to
> > > conjunctive queries. I will use a "pidgin" LaTeX
> > > first-order logic notation for this. I'll use _:x for anonymous
> > > individuals, and I'll use != for inequality (DifferentFrom)
> > > assertions and & for conjunction.
> > >
> > >
> > > Imagine you have an ABox A containing the following assertions:
> > >
> > > (1)  hor(_:1,_:2)
> > > (2)  ver(_:2,_:3)
> > > (3)  ver(_:1,_:4)
> > > (4)  hor(_:4,_:5)
> > > (5)  _:3 != _:5
> > >
> > > Under the traditional semantics, anonymous individuals are actually
> > > existentially quantified variables. Hence, the ABox A is
> > > actually equivalent to the following first-order formula \varphi:
> >
> > Hello,
> >
> > But is it possible to have the above statements in OWL 1.1? Since _:3
> and
> > _:5 are anonymous how can you refer to them in this difference assertion
> > (!=)?
> >
> > Greetings,
> > -gstoil

Received on Friday, 9 November 2007 11:07:54 UTC