Re: Action-164 suggestions (again) for unnamed individuals *in addition* to bnodes

On Jul 2, 2008, at 7:12 AM, Bijan Parsia wrote:

> On 2 Jul 2008, at 12:00, Alan Ruttenberg wrote:
>
>> Fulfilling action-164, Here is a pointer to the email when I first  
>> suggested we consider supporting both bnodes and unnamed (for the  
>> user) individuals.
>>
>> http://lists.w3.org/Archives/Public/public-owl-wg/2007Nov/0214.html
>>
>> Snippet, omitting unrelated, but not current suggestions.
>>
>> It seems to me that we could actually support both.
>>
>>> Individual(type(owl:Thing)) could be a skolem
>>> SomeIndividual(type(owl:Thing)) could be an existential.
>
> This imposes a tree like restriction on the first.

Good point!  The syntax would need to "name" the unnamed individual.

So better would be:

UnnamedIndividual([handle] type(owl:Thing))

where handle is name for the individual that has scoped within the  
ontology only.


>> That is, we could offer two forms of anonymous individual  
>> constructors. Neither would specify a name. One form of  
>> constructor would allocate a unique (to exceedingly high  
>> probability) name. The other would use a bnode, interpreted using  
>> the usual existential semantics.
>>
>> Tree-shape restrictions would hold for the existentials, but not  
>> for the other kinds of anonymous individuals.
>
> This would make entailment undecidable.

Why? The individuals created by the "UnnamedIndividual()" constructor  
are not really anonymous - they are named, just not by the user. So  
we have tree-shaped restrictions for the existentials, as in OWL 1,  
and arbitrary graphs of named individuals, as before.

> It also doesn't address the legacy issue that people use bnodes as  
> if they were skolem. We could consider evangelizing not using  
> bnodes in RDF when skolem semantics were meant, but I don't see  
> that working well anytime soon without a *big* push.

True. However my action wasn't to address this. It is certainly an  
important element in our discussion of what decision to make, though.

Best,
Alan

>
> Cheers,
> Bijan.
>