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RE: UFDTF Metamodeling Document

From: Conrad Bock <conrad.bock@nist.gov>
Date: Fri, 30 Nov 2007 13:28:25 -0500
To: "'Peter F. Patel-Schneider'" <pfps@research.bell-labs.com>
Cc: <alanruttenberg@gmail.com>, <ekendall@sandsoft.com>, <public-owl-wg@w3.org>, <cawelty@gmail.com>
Message-ID: <1b5301c8337e$cbc39eb0$b3200681@MEL.NIST.GOV>

Peter,

 >  >  >  An RDF triple contains three components:

 >  >  >      * the subject, which is an RDF URI reference or a 
 >  >  >        blank node
 >  >  >      * the predicate, which is an RDF URI reference
 >  >  >      * the object, which is an RDF URI reference, a literal 
 >  >  >        or a blank node

 >  > BTW, the question above would not come up without review of the
 >  > ODM metamodel.  It gives a less ambiguous description of the
 >  > above, which is just text that doesn't have the detail of "must",
 >  > and "at least one", etc.

 >  Umm, how is the text above ambiguous?  To me, it clearly states that
 >  an RDF triple has to have three components, namely one subject, one
 >  predicate, and one object.  I suppose that it could have been made
 >  more pedantic by adding "MUST" and "exactly", but I don't think that
 >  this change would make the situation any clearer (and I am known for
 >  being very picky about being precise in definitions).

It's just natural language.  The mandatoriness or optionality of
a list elements in English just can't be reliabily determined.

 >  In any case there a lots of places in the RDF Semantics document
 >  where it is clearly shown that an RDF triple has to have all three
 >  components, including the places where the basic semantics of RDF is
 >  formally defined.

Well, I'm glad you're sure.  The purpose of *widely* agreed metamodels
is that everyone is sure.

 >  > This is another reasong it is critical to have community-wide
 >  > agreement on the OWL and RDF metamodels, rather than multiple ones
 >  > from multiple standards bodies.  We won't get to that agreement by
 >  > ignoring each other's metamodels.  Issue 82 was worded
 >  > specifically for harmonization, rather than divorce.  This is a
 >  > perfect time to do it, before finalization of the ODM and
 >  > recommendation of OWL 1.1.

 >  Well, I'm not sure about this.  

 >  OWL is already a W3C recommendation.  It seems to me that the only
 >  possible stance is that any OMG metamodel for OWL has to reflect
 >  what is in the W3C recommendation.

Agreed, and that was and is the goal for it, and would be the result of
having one metamodel agreed on by both communities.  The OMGers don't
want to change RDF/OWL through the OMG process, just metamodel it.

 >  The situation with OWL 1.1 is exactly similar.  OWL 1.1 exists as a
 >  member submission to W3C.  If the OMG wants to have a metamodel for
 >  OWL 1.1 then it again has to submit to what is.  The structural
 >  specification for OWL 1.1 is part of OWL 1.1.  

Well, not as a recommendation.

 >  I don't see any reason for the OWL 1.1 stuctural specification to be
 >  changed to match errors in the OMG metamodel for OWL.  

Why would it need to match errors in the OMG metamodel?  See below.

 > I don't see any overarching reason for the OWL 1.1 structural
 > specification to be significantly changed to align it with the OMG
 > specification for OWL, as the structural specification is targetted
 > towards extracting the structure of an OWL 1.1 ontology in a way that
 > is useful for building OWL 1.1 tools.

Issue 82 doesn't specify which metamodel changes how much, only that
they be the same.

 >  Even the situation with the OWL WG is quite similar.  The OWL WG is
 >  supposed to come up with an update to the W3C OWL recommendation.
 >  Alignment with the OMG metamodel for OWL is at best a secondary
 >  concern.  Certainly there is no reason to make a sub-optimal design
 >  choice for the updated OWL just to match something in the OMG
 >  metamodel for the old OWL.

It's a primary concern for those using structual models.  If you're not
one of them, of course it would appear secondary.

 >  In any case, I certainly don't see any reason for the OWL WG to
 >  change its schedule to meet any OMG schedule.

I don't think this would be necessary.

Conrad
Received on Friday, 30 November 2007 18:29:19 GMT

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