# RE: Blank Node Equality Question

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Mon, 21 Jul 2003 13:53:49 +0200
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>, <jjc@hplb.hpl.hp.com>

Message-ID: <BHEGLCKMOHGLGNOKPGHDGENGCBAA.jjc@hpl.hp.com>
```

> > Given the question statement, and assuming the initial graph G is
> > consistent, then
> >
> > G
> > _:a owl:sameIndividualAs _:b .
> >
> > is consistent.
>
> Not so.  (At least not in Jeremy's reformulation.)
>

Agreed.
Peter's example here then gives what DanBri seem to be interested in of two
blank nodes denoting twins.
i.e. we cannot tell them apart but they are different.

The example is in OWL Full because OWL DL does not permit oneOf over blank
nodes. Can this be reformulated in OWL DL?

Jeremy

> Consider the following graph
>
> _:a rdf:type owl:Thing .
> _:b rdf:type owl:Thing .
>
> ex:foo rdf:type owl:Class .
> ex:foo owl:oneOf _:l1 .
> _:l1 rdf:type rdf:List .
> _:l1 rdf:first _:a .
> _:l1 rdf:rest _:l2 .
> _:l2 rdf:type rdf:List .
> _:l2 rdf:first _:b .
> _:l2 rdf:rest rdf:nil .
> ex:foo owl:oneOf _:l3 .
> _:l3 rdf:type rdf:List .
> _:l3 rdf:first _:b .
> _:l3 rdf:rest _:l4 .
> _:l4 rdf:type rdf:List .
> _:l4 rdf:first _:a .
> _:l4 rdf:rest rdf:nil .
>
> ex:john rdf:type owl:Thing .
> ex:john rdf:type _:r1 .
> _:r1 rdf:type owl:Restriction .
> _:r1 owl:onProperty ex:p .
> _:r1 owl:cardinality "2"^^xsd:NonNegativeInteger .
>
> ex:p rdf:type owl:ObjectProperty .
> ex:p rdf:range ex:foo .
>
> This entails
>
> _:a owl:differentFrom _:b .
>
>
> Peter F. Patel-Schneider
> Bell Labs Research
> Lucent Technologies
>
```
Received on Monday, 21 July 2003 07:54:18 GMT

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