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Re: question about DL/Lite semantics

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 04 Jun 2003 16:00:02 -0400 (EDT)
Message-Id: <20030604.160002.85524573.pfps@research.bell-labs.com>
To: jjc@hpl.hp.com
Cc: www-webont-wg@w3.org

From: Jeremy Carroll <jjc@hpl.hp.com>
Subject: question about DL/Lite semantics
Date: Mon, 2 Jun 2003 12:13:23 +0300

> 
> 
> On one of my homework assignments after the beer session I've got a little bit 
> stuck considering the following entailments according to the direct semantics
> 
> Does
> 
> Class( <foo> annotation( <a> <bar> ) )
> AnnotationProperty( <a> )
> Class( <bar> )
> 
> entail
> 
> AnnotationProperty( <a> )
> Class( <foo> annotation( <a> individual() ) )
> 
> ?
> 
> If not, why not?

[...]

> Jeremy

This message from Jeremy points out an issue with the direct semantics.  In
my haste to put in annotations, I make them relate individuals to
individuals.  This has problems when the domain is very small.  For example

AnnotationProperty(ex:a)
ObjectProperty(ex:p Symmetric)
SubClassOf(owl:Thing restriction(ex:p value(ex:x)))
Individual(ex:x restriction(ex:p cardinality(1)))
Class(ex:c1 annotation(ex:a ex:a))

entails

AnnotationProperty(ex:a annotation(ex:a ex:a))

because there is only one individual (the interpretation of ex:x).

However, this is not a valid entailment in the RDF semantics.


I propose to fix this by modifying the direct semantics to admit ``junk''
elements of the domain, i.e., elements of the domain that are not
individuals.  This makes the direct semantics more ugly, but more like the
RDF semantics.

One side effect would be that Jeremy's entailment above would not hold,
because <bar> would not have to be an individual.

Comments?

Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies
 
Received on Wednesday, 4 June 2003 16:00:18 GMT

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