# Re: [OWL compatibility] #, ## in OWL compatibility

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Thu, 10 Sep 2009 10:23:04 -0400
To: Jos de Bruijn <debruijn@inf.unibz.it>
Cc: RIF <public-rif-wg@w3.org>
I think solution 1 is unacceptable because it hides something very important.
While reading SWC, I assumed that things are as in Solution 3 until you told me
otherwise.

Solution 2 is bad because it means adding lengthy explanations to explain an
exception, which is easy to fix directly.

While we are at it, I think we can fix one other weakness here. Assuming that
we go with Solution 3, the relationship between rdfs:subclassOf and ## will be
that  rdfs:subclassOf is a superset of ## for RDFS, OWL Full, and OWL-DL. I

{(A,B) | A rdfs:subclassOf B and A != B on the RDF/OWL side}
subset {(A,B) | A##B on the RIF side}

This way subclass relationships on the RDF/OWL side would imply the same on the
RIF side for unequal classes.

michael

On Thu, 10 Sep 2009 11:16:56 +0200
Jos de Bruijn <debruijn@inf.unibz.it> wrote:

> In RIF-RDF combinations, there is a one-to-one correspondence between
> rdf:type statements and # statements, and ## statements imply
> rdfs:subClassOf statements, so:
>
> a#b  iff a[rdf:type -> b]   and
> a##b implies a[rdf:subClassOf -> b]
>
>
> These correspondences also hold in RIF-OWL Full combinations, since
> their semantics simply extends the semantics of RIF-RDF combinations.
>
> Now, since the semantics of RIF-OWL DL combinations is completely
> different, these correspondences do not automatically carry over.  In
> fact, in such combinations there is no relationship between # and ##
> statements in RIF, on the one hand, and typing and subclass statements
> in OWL DL, on the other.  A minimalistic approach was taken in the
> specification of the semantics of RIF-OWL DL combinations:
> -OWL class membership statements A(?x) correspond to RIF statements
> ?x[rdf:type -> A]
> -property value statements R(?x,?y) correspond to RIF statements ?x[R -> ?y]
>
> There are no further correspondences between statements in OWL DL and in
> RIF.  However, some users may expect to be able to use # and ##
> statements to access OWL class membership; the document currently does
> not explain that this is not possible.
> We could do one of three things:
> 1- leave things as they are, assuming that # and ## are not of interest
> to users of RIF-OWL DL combinations
> 2- explain the use of # and ## in the document (this would certainly not
> be a substantive change, so we should not run into procedural problems)
> 3- define the semantics of # and ## in RIF-OWL DL combinations in a
> similar fashion as in RIF-RDF combinations: a one-to-one correspondence
> between # and OWL class membership statements and implication between ##
> and OWL subclassing.  Technically, this is not a problem.  In principle,
> it would be a substantive change, but we might be able to argue that it
> was a bug in the specification.
>
> I am fine with any of the options.  Clearly, option 1 would be least
> work for me, followed by option 3.
> Opinions?
>
> Best, Jos
Received on Thursday, 10 September 2009 14:23:54 UTC

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