RE: Comment on RDF Mapping: variables in sequence pattern

[not answered to comment list, but to wg list]

>-----Original Message-----
>From: public-owl-comments-request@w3.org [mailto:public-owl-comments-
>request@w3.org] On Behalf Of Mike Smith
>Sent: Tuesday, January 06, 2009 3:53 PM
>To: public-owl-comments@w3.org
>Subject: Comment on RDF Mapping: variables in sequence pattern
>
>
>While verifying some WebOnt test cases against the RDF to structural
>mapping defined at [1], 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 [1]).  I found this
>problematic, particularly when trying to avoid things like cyclic
>lists (as in the nonconclusion ontology of [I5.5-006]).

I think that this was, in OWL 1, only a testcase for the OWL Full
comprehension principles to be implemented correctly (marked as "FULL
extracredit" in the original test; and yes, implementing the comprehension
principles would have deserved extracredit, I guess ;-)). The comprehension
principles are non-normative in OWL 2 Full, so this testcase can probably be
dropped. 

I also think that this is not an appropriate testcase for the direct
semantics (it's marked as such), because I don't see that the RHS graph in
that testcase is a valid OWL 2 DL ontology in RDF graph form. It is simply
some dangling list expression, not being the argument list of any other
language construct, so how would this be mapped to Functional Syntax at all?


Apart from this, I would be pretty reluctant on having tests for stuff like
avoiding circular RDF lists and the like. I would say that it is the fault
of the RDF spec to allow such strange things to happen with lists, it should
not be treated by OWL testcases, IMHO.

>I believe that adding the constraint to the mapping document will
>clarify the expected behavior.

Perhaps, keeping things as they are might be sufficient. Are implementers
and ontology authors/users expected to have trouble with the current state?

Cheers,
Michael

>
>--
>Mike Smith
>
>Clark & Parsia
>http://clarkparsia.com/
>
>[1] http://www.w3.org/TR/2008/WD-owl2-mapping-to-rdf-
>20081202/#Mapping_from_RDF_Graphs_to_the_Structural_Specification
>[I5.5-006] http://km.aifb.uni-
>karlsruhe.de/projects/owltests/index.php/TestCase:WebOnt-I5.5-006
>


--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
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Email: Michael.Schneider@fzi.de
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FZI Forschungszentrum Informatik an der Universität Karlsruhe
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