Re: Small problem with Expression.owl

Getting back to the original issue, I now think we should just do this:

<Condition rdf:ID="AlwaysTrue" />

Done.

This has the added advantage of being usable with any expression 
language. It requires the OWL-S processor to be aware of this special 
instance, but so does the previous version, so no difference there.

Daniel


Daniel Elenius wrote:

> Now that SWRL-Conditions aren't literals anymore, the following, in 
> the 1.2 Expression.owl, makes that file
> OWL Full (since we are "redefining rdf:nil"):
>
> <SWRL-Condition rdf:ID="AlwaysTrue">
>  <rdfs:label>Always True</rdfs:label>
>  <rdfs:comment>
>    An empty AtomList always evaluates to true. Note that this is not 
> equivalent to specifiying no
>    precondition. Due to open-world semantics of OWL, it would not be 
> possible to distinguish
>    having no precondition from not knowing the precondition. We would 
> need to specify a
>    cardinality 0 restriction on precondition property to indicate that 
> there is no precondition
>    which would be also valid.
>  </rdfs:comment>
>  <expressionLanguage rdf:resource="&expr;#SWRL"/>
>  <expressionObject>
>    <swrl:AtomList rdf:about="&rdf;#nil"/>
>  </expressionObject>
> </SWRL-Condition>
>
> An easy solution would be to move the AlwaysTrue instance to a 
> separate file, which would only be imported by OWL-S services that use 
> SWRL. That way other services could still stay in OWL DL. Perhaps a 
> little ugly to have a file with just one instance though.
>
> Daniel
>
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Received on Thursday, 23 June 2005 16:51:19 UTC