- From: pat hayes <phayes@ai.uwf.edu>
- Date: Wed, 9 Oct 2002 12:25:22 +0100
- To: www-webont-wg@w3.org
The final discussion of owl:imports at the f2f kind of melted down, for which I take much of the blame. Afterwards it occurred to me how to phrase the statement everyone wanted to make about owl:imports so as to avoid all the unwanted implications. Not surprisingly, it is easy, and it has to do with the model theory: ------------ owl:imports BBB is true in an interpretation I just when the owl KB gotten by dereferencing BBB is true in I, OR if there is no such owl KB. ------------- If there isn't any such document, therefore, this is just plain true, which makes it kind of vacuous in that case. But if there is, then the imports assertion amounts to the same as asserting that KB inside this KB. So in this case: A: socrates rdf:type B:human . B: human rdfs:subClassOf mortal . C: owl:imports B socrates rdf:type B:human then A does not entail D: socrates rdf:type B:mortal but C does, provided of course that the imports worked; since in that case the imports statement is only true in interpretations which make B true. If the imports failed, then C wouldnt entail D, but not because 'entails' changes its meaning, but because in that case asserting C doesnt amount to saying as much as it does when the imports did work. In effect, C gets smaller when the imports fails. Note, this uses the usual notion of entailment, so entailment is not subject to the whims of 404 errors. Also note, this does not say that anyone is under any obligation to do anything (such as load a file) . It only says what is being claimed to be true. Pat -- --------------------------------------------------------------------- IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32501 (850)291 0667 cell phayes@ai.uwf.edu http://www.coginst.uwf.edu/~phayes
Received on Wednesday, 9 October 2002 07:24:43 UTC