|While verifying some WebOnt test cases against the RDF to structural mapping defined at [Mapping from RDF Graphs], I noticed that there is no constraint preventing variables within the sequence pattern from matching the same node (see the second row of Table 3 at [Mapping from RDF Graphs]). I found this problematic, particularly when trying to avoid things like cyclic lists (as in the nonconclusion ontology of [TestCase:WebOnt-I5.5-006]).
I believe that adding the constraint to the mapping document will clarify the expected behavior.
PeterPatel-Schneider 19:56, 7 January 2009 (UTC) Mike has identified a real problem. I believe that the best solution is to add something like:
No blank node can be used in more than once in these patterns. (This means that all lists are non-cyclic and do not share tails.)
Just before Table 3 in RDF Mapping. This would require a post LC justification.
PeterPatel-Schneider 13:52, 27 January 2009 (UTC) draft response:
Thank you for your comment http://lists.w3.org/Archives/Public/public-owl-comments/2009Jan/0002.html on the OWL 2 Web Ontology Language last call drafts.
You have indeed identified a bug in the mapping from RDF to the functional syntax. The WG has decided to address this mapping by adding an extra condition to the mapping from RDF graphs to the functional syntax that prohibits the multiple use of list nodes. This outlaws malformed lists, including lists with internal loops and lists that cross. This is a change to the technical specification of OWL 2.
The changes to the OWL 2 documents are:
Please acknowledge receipt of this email to <mailto:firstname.lastname@example.org> (replying to this email should suffice). In your acknowledgment please let us know whether or not you are satisfied with the working group's response to your comment.
Regards, Peter F. Patel-Schneider on behalf of the W3C OWL Working Group