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Semantics of owl:imports

From: Jerome Euzenat <Jerome.Euzenat@inrialpes.fr>
Date: Sat, 9 Nov 2002 22:15:37 +0100
Message-Id: <a05111b04b9f2c161b833@[194.199.20.189]>
To: pat hayes <phayes@ai.uwf.edu>, www-webont-wg@w3.org

Hello,

First, I am not fanatical of interpreting owl:import as a triple just 
like any other assertion. I think that this could be just like 
owl:ontology (as in a recent P. Hayes mail), not in the graph but 
replaced by its content (I understand that this cause problems 
because if RDF does not understand this, then RDF and OWL 
interpretations will diverge).

This said, I am impressed by the logical jewellery that Pat is 
deploying for accomodating this. For me it's breathtaking. I see that 
this is a tricky game to arrange everything for RDF, RDFS and OWL.

I raise here an objection that I am not sure is valid (because I do 
not master enough the semantics of RDF and OWL) but I am sure Pat can 
quickly answer.

The import are reintroduced as triple with a specially designed 
semantics. In the short story:
>Therefore, a document containing an I-import triple entails anything 
>which is entailed by the imports closure of the document referred to 
>be the object, in the usual sense of 'entails'.

This looks like any one has abandonned the idea of 'reifying' 
statements and applying negation of these?

If not, what could be the negation of an import?
The problem that should be well known among non-compositionnal (non 
verifunctionnal if I remember) constructs is if their negation 
affects the importing action itself or its results (i.e., if the 
ontology does not import or if it imports the negation of the 
imported statements). The negation of the sentence above suggest that 
the document should entail the negation of what is entailled by the 
import closure.

Does it force to NOT entail the entailments of the import closure?

If not, then we have NOT(NOT(IMPORT(http://bla))) which is not the 
same as IMPORT(http://bla). (Perfectly fine, but we've got to know 
this).

Another naïve remark: is it possible, in OWL/Full or RDFS to subclass 
owl:Ontology and to apply such rules as:

<owl:Class rdf:ID="theCrazyOne">
	<rdfs:subClassOf rdf:resource="&owl;Ontology"/>
	<rdfs:subClassOf>
		<owl:complementOf/>
			<owl:Restriction>
				<owl:onProperty rdf:resource="&owl;imports"/>
				<owl:hasValue rdf:resource="http://bla"/>
			</owl:Restriction>
		</owl:complementOf>
	</rdfs:subClassOf>
</owl:Class>

Sounds like the class of ontologies that do not import a particular 
resource. This can be a perfectly meaningfull concept. But I am not 
sure of its meaning that can is dependent of the answer to the 
question above.

Please forgive these unsufficiently informed interogations.
-- 
  Jérôme Euzenat                  __
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Received on Saturday, 9 November 2002 16:28:22 GMT

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