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[LC response] To Jeremy Carroll (JC2 on owl:real)

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Mon, 18 May 2009 17:58:32 +0100
Message-Id: <3FBC40A2-3139-40EA-A2C5-4D517D39C175@cs.man.ac.uk>
To: Jeremy Carroll <jeremy@topquadrant.com>, public-owl-comments@w3.org
Dear Jeremy,

Thank you for your comment
     <http://lists.w3.org/Archives/Public/public-owl-comments/2009May/ 
0013.html>
on the OWL 2 Web Ontology Language last call drafts.

To address your points in turn:

* According to a normative part of RDF Concepts,
     <http://www.w3.org/TR/rdf-concepts/#section-Datatypes>:

"Each member of the value space may be paired with any number  
(including zero) of members of the lexical space ...

... RDF may be used with any datatype definition that conforms to  
this abstraction, even if not defined in terms of XML Schema."

So here RDF datatypes can have an empty lexical space and a trivial  
lexical-to-value mapping, as in owl:real.

This is contradicted in RDF Semantics, <http://www.w3.org/TR/rdf-mt/ 
#dtype_interp>:

"Formally, a datatype d is defined by three items:

      1. a non-empty set of character strings called the lexical  
space of d; ...."

There does not appear to be any technical reason for this prohibition  
on empty lexical spaces in RDF Semantics. For any new datatype, RDF  
systems must be upgraded to recognize which strings are ill-formed  
for that datatype. For an empty datatype, they must simply treat any  
string as ill-formed which is the desired behavior here. Thus,  
owl:real is eminently compatible with RDF systems and technically in  
compliance with one of the definitions supplied by the  
specifications. The Working Group will send an error report about  
this contradiction to the appropriate list.

* There are no negative effects from requiring the OWL 2 domain of  
discourse to be uncountable. The fundamentals of the semantics are  
unchanged; there is no need to significantly change implementations.

* The working group has discussed your document extensively and  
addressed the issues it raised. It is in fact partly in response to  
the concerns mentioned there that OWL 2 has owl:real (and  
owl:rational) as support for avoiding the problematic use of floating  
point numbers, not just for n-ary data predicates but also as a  
matter of modeling cleanliness.
Given these considerations, the Working Group has decided to make no  
change in response to your comment.

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, and whether you  
would like us to record you as Formally Objecting to the advancement  
of OWL 2 along the W3C Recommendation Track. (Note that according to  
the W3C Process, Formal Objections are made by individuals, not  
organizations.)

Regards,
Bijan Parsia
on behalf of the W3C OWL Working Group
Received on Monday, 18 May 2009 16:54:36 GMT

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