Re: Update on PROV-O OWL file (Action item 55)

On Feb 16, 2012, at 21:45 , Satya Sahoo wrote:

[snip]
> 
> ie, using a union of classes as part of the domain is not allowed. The rules also express this. And, although a layperson in terms of hard core logic, I can see why: if a resource is the subject of that property, a simple rule engine _cannot_ find out which of the constituents of the union it belongs to. Ie, it cannot make any intelligent deduction.
> 
> Can you please clarify the above point - reasoners do consistency check (class with no possible instance) and classification (identify inferred sub/super class), the above example of inferring class membership seems to be a RDFS entailment. 

Correct. Reasoners, say, DL reasoners do this stuff, but those are inferences on the classes themselves. However, again from my non-logician perspective, OWL 2 RL concentrates more on the instance data, on the inferences drawn on individuals. The OWL 2 RL Rules do that, and they do it in a way that they can be easily implemented either directed or through some rule engine. And that is where the problem comes in.

If I have 

provo:hadTemporalEngine rdfs:domain A .

then the rules can be used for the inference :

x provo:hadTemporalEngine y . => x rdf:type A .

but if I have

provo:hadTemporalEngine rdfs:domain [ owl:union ( A,B,C) ] .

then, again in the case of 

x provo:hadTemporalEngine y . => x rdf:type A .

there is no rule that would help me to make any kind of statement on the type of 'x' v.a.v. A, B, or C. In other words, if I simply use the OWL 2 RL Rules, that domain statement does not provide any information that the reasoner could exploit on the data.

I hope this is clearer (and that I am right:-)

Cheers

Ivan


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Ivan Herman, W3C Semantic Web Activity Lead
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