PeterPatel-Schneider 20:58, 19 February 2009 (UTC)
[Draft Response for LC Comment 32:] CO1
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on the OWL 2 Web Ontology Language last call drafts.
Arbitrary RDF graphs can include constructs that have surprising consequences. The reasons for these are many and varied, including effects on the "syntax" of OWL 2. Because there are so many ways in which the rules could be incorrect, the working group has decided not to exactly characterize how the incorrectness arises, but instead has included a mention that arbitrary RDF graphs can affect the underpinnings of OWL, as follows:
For ontologies satisfying the syntactic constraints described in Section 4.2, a suitable rule-based implementation will have desirable computational properties; for example, it can return all and only the correct answers to certain kinds of query (see Section 4.3 and [Conformance]). Such an implementation can also be used with arbitrary RDF graphs. In this case, however, these properties no longer hold — in particular, it is no longer possible to guarantee that all correct answers can be returned, for example if the RDF graph uses the built-in vocabulary in unusual ways.
There are an infinite number of RDFS axiomatic triples, so including them all in the OWL 2 RL rules does not directly lead to an effective rule implementation. There are some RDFS rules that produce consequences that are not relevant to the conclusions guaranteed by Theorem PR1. Listing all the "deficiencies" is not particularly easy, and would probably only confuse the issue. The working group has therefore decided not to be more explicit in the preamble to Theorem PR1.
The diffs can be found at ..........
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Regards, Peter F. Patel-Schneider on behalf of the W3C OWL Working Group
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