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Re: OWL abstract syntax: -lite, -dl restrictions

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Fri, 09 May 2003 15:00:27 -0400 (EDT)
Message-Id: <20030509.150027.63218251.pfps@research.bell-labs.com>
To: gk@ninebynine.org
Cc: public-webont-comments@w3.org

From: Graham Klyne <gk@ninebynine.org>
Subject: OWL abstract syntax: -lite, -dl restrictions
Date: Tue, 06 May 2003 17:29:37 +0100

> With reference to:
>    http://www.w3.org/TR/owl-semantics/syntax.html#2.3.1.2
> and
>    http://www.w3.org/TR/owl-semantics/syntax.html#2.3.2.3
> 
> I see that for OWL-lite:
> [[
> restriction ::= 'restriction(' datavaluedPropertyID 
> dataRestrictionComponent ')'
>              | 'restriction(' individualvaluedPropertyID 
> objectRestrictionComponent ')'
> ]]
> 
> But for OWL-DL:
> [[
> restriction ::= 'restriction(' datavaluedPropertyID 
> dataRestrictionComponent { dataRestrictionComponent } ')'
>              | 'restriction(' individualvaluedPropertyID 
> objectRestrictionComponent { objectRestrictionComponent } ')'
> ]]
> 
> Is it intended that a restriction may have only one component in OWL-lite?

Yes, this is intended.

> This restriction (sic) seems rather pointless, as I think an axiom naming a 
> class can be repeated with multiple single-component restrictions to 
> achieve the same effect.

The more-complex construction in OWL DL is strictly convenience, as there
it can always be replaced by an intersection.  However, in OWL Lite, this
replacement is not always (easily) possible, leading to difficulties as to
just what can be said in OWL Lite.

> Also, I note that OWL-lite restrictions do not include the single-value 
> form of restriction "Value( _ )".  Is this intended?

Yes, this is as intended.  The Value(_) construction augments the
expressive power of the language and was not put in OWL Lite for this
reason.   

> (I see no purpose in raising a formal issue for this.)
> 
> #g

Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies
Received on Friday, 9 May 2003 15:00:39 GMT

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