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Re: [LC response] To Jeff Heflin

From: Ian Horrocks <ian.horrocks@comlab.ox.ac.uk>
Date: Fri, 4 Sep 2009 14:35:57 +0100
Message-Id: <616072B3-9DC6-414C-84C7-D72C2E239744@comlab.ox.ac.uk>
Cc: public-owl-comments@w3.org
To: Jeff Heflin <heflin@cse.lehigh.edu>
Dear Jeff,

Thank you for your comment
on the OWL 2 Web Ontology Language last call drafts.

Regarding deprecation, "essentially the same" refers to the fact  
that, as mentioned in the Quick Reference Guide [1], <anyIRI  
owl:deprecated "true"^^xsd:boolean> is equivalent to <someClass  
rdf:type DeprecatedClass>. Respecting the mapping, according to the  
OWL S&AS [5], each triple of the form

  classID rdf:type owl:DeprecatedClass .
must be accompanied by a triple of the form

  classID rdf:type owl:Class .
The situation is similar for deprecated properties. Consequently, the  
OWL 2 mapping from RDF Graphs to the Structural Specification [6] is  
backwards compatible with OWL.

Regarding profiles, the QL profile in particular aims at providing  
performance that is comparable to the performance of database  
systems. Achieving this in practice will require some care in the  
design of both query answering systems and the applications that use  
them. In this respect we do not believe that OWL QL is significantly  
different to relational database systems, where good performance at  
large scale also requires major system engineering efforts as well as  
care in the design of the schema. Some preliminary but reasonably  
encouraging evaluations of query answering performance using DL-Lite  
can be found in [2], [7].

As far as consistency checking is concerned, in QL this can be  
implemented by a union of queries that is worst case polynomial in  
the size of the schema (TBox), where each query is is rather simple,  
and where the overall size of the query depends on the position and  
number of negations (see [3] page 405). When checking in the presence  
of updates, it is even simpler as one can ground parts of the query  
and also determine which disjuncts are relevant.

Regarding arithmetic operations, I apologize for having omitted the  
pointer -- the latest version of the proposed Working Group Note can  
be found at [4].

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.

Ian Horrocks
on behalf of the W3C OWL Working Group

[1] http://www.w3.org/2007/OWL/wiki/ 
[2] http://www.abdn.ac.uk/~csc280/PaTh07.pdf
[3] D. Calvanese, G. De Giacomo, D. Lembo, M. Lenzerini, and R.  
Rosati. Tractable reasoning and efficient query answering in  
description logics: The DL-Lite family. J. of Automated Reasoning, 39 
(3):385429, 2007.
[4] http://www.w3.org/2007/OWL/wiki/ 
[5] http://www.w3.org/TR/owl-semantics/mapping.html
[6] http://www.w3.org/2007/OWL/wiki/ 
[7] http://www.inf.unibz.it/%7ecalvanese/papers/calv-etal-SDKB-2008.pdf
Received on Friday, 4 September 2009 13:37:02 UTC

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