LC Responses/CO1

PeterPatel-Schneider 20:58, 19 February 2009 (UTC)

[Draft Response for LC Comment 32:] CO1

Dear Chimezie,

Thank you for your message

 http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0039.html

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

No trees were known to have been harmed in the preparation of this response.