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Re: ACTION-280 completed

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Thu, 5 Feb 2009 09:50:57 +0000
Message-Id: <28635BD9-BA0D-4931-BB30-D5AFE35A267C@cs.man.ac.uk>
To: public-owl-wg Working Group <public-owl-wg@w3.org>

I tweaked it just a little bit.

Cheers,
Bijan.

To: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
CC: public-owl-comments@w3.org
Subject: [LC response] To Frank van Harmelen

Dear Frank,

Thank you for your comment
      <http://lists.w3.org/Archives/Public/public-owl-comments/ 
2009Jan/0037.html>
on the OWL 2 Web Ontology Language last call drafts.

First, we'd like to note that the shift in the specification from  
using truly blank nodes to using nodeIDs is not a change to the  
*language* but merely a change in the *presentation* of the language.  
No new capability, esp. from the RDF perspective, has occurred. In  
the old specification:

     <http://www.w3.org/TR/owl-semantics/>
the patterns of admissible blank nodes (roughly, tree like patterns  
that can be mapped to nested someValuesOf) could be specified without  
recourse to nodeIDs due to the (tree-like) frame structure of  
Abstract syntax constructions. Unfortunately, this is not possible in  
the new functional syntax, hence we must make use of a different  
mechanism to express the same point. Additionally, we believe there  
is value in having explicit nodeIDs, borrowing from RDF, since it  
makes it clear that there is an actual, significant syntax item there.

Here is an example of the difficulty:

(Remember, in <http://www.w3.org/TR/owl-semantics/syntax.html#2.2>:

    """The syntax here is set up to somewhat mirror RDF/XML syntax  
[RDF Syntax] without the use of rdf:nodeID.""")
ABSTRACT SYNTAX:

   Individual(anObjectProperty
                 Individual(aDataProperty "foo"))
TURTLE:

   [anObjectProperty
          [aDataProperty "foo"]]
TURTLE WITH NODEIDS:

    _:x anObjectProperty _:y.
    _:y aDataProperty "foo".
FUNCTIONAL SYNTAX:

   PropertyAssertion(anObjectProperty _:x _:y)
   PropertyAssertion(aDataProperty _:y "Foo")
This is essentially an issue of surface syntax used in the  
specification. The FS is designed such that axioms in the FS  
correspond to axioms in first order logic (which makes various  
specification issues easier). This makes it impossible to use  
implicit BNodes. Furthermore, given the tradition of using nodeIDs in  
RDF, we feel we are well within best practice and, in fact, think  
that this style makes what's going on substantively clearer.

Accordingly, the working group has decided not to make the change  
you've suggested.

Please acknowledge receipt of this email to <mailto:public-owl- 
comments@w3.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,
Bijan Parsia
on behalf of the W3C OWL Working Group
Received on Thursday, 5 February 2009 09:47:28 GMT

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