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Re: Issue #pan-01 Re: Comment on Last Call Working Draft of RDF Semantics document concerning treating classes and properties as objects

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 20 Feb 2003 13:24:13 -0600
Message-Id: <p05111b20ba7ad3047dbc@[]>
To: "Jeff Z. Pan" <pan@cs.man.ac.uk>
Cc: www-rdf-comments@w3.org

>----- Original Message -----
>From: "Brian McBride" <bwm@hplb.hpl.hp.com>
>To: "Jeff Z Pan" <pan@cs.man.ac.uk>; <www-rdf-comments@w3.org>
>Sent: Tuesday, February 18, 2003 11:35 AM
>Subject: Issue #pan-01 Re: Comment on Last Call Working Draft of RDF Semantics
>document concerning treating classes and properties as objects
>>  Jeff,
>>  With Pat responding that your comments are not editorial, I'm going to try
>>  to identify the comments you are making for consideration by the WG.
>>     http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0283.html
>>  At 21:15 14/02/2003 -0800, Jeff Z Pan wrote:
>>  >Recent research (http://dl-web.man.ac.uk/rdfsfa/paper.htm) has shown that
>>  >RDF Schema (RDFS) has a non-standard metamodeling architecture, which makes
>>  >some elements in the model have dual roles in the RDFS specification.  As a
>>  >result, this can be confusing and difficult to understand and,  more
>>  >importantly, the specification of its semantics requires a non-standard
>>  >model theory - RDF MT. RDF MT justifies dual roles by "treating classes and
>>  >properties as objects", which seems to be ok within RDFS. However, this
>>  >leads to semantic problems when we extend RDFS with more expressive FOL
>>  >constructs, and extend RDF MT to the so called ``RDF+ MT'' to give meaning
>>  >to this extended language:
>>  Ok - I think you are saying you are trying to extend RDF(S) to some
>>  (proper?) subset of FOL and are having problems.  Yes?  The rest of this
>>  message is an explanation of the difficulties you are experiencing.
>It also suggests that it might be a good idea to also locate a sub-language of
>(e.g. RDFS(FA)) such that when FOL languages are built on it, they can have
>their traditional semantics, and the existing highly optimised 
>implementations of
>FOL (or its decidable subsets) can be employed.

It would be very helpful if you could be more precise. My 
understanding is that RDFS already has this character, if one 
interprets the phrases 'built on' and 'can be deployed' 
appropriately, and that the existence of OWL illustrates this.

Your comment can be interpreted, therefore, in several ways.

(1) You do not agree with this understanding - in which case, it 
would be helpful if you could document the problems in some detail, 
or give examples. (All the issues you mentioned in your first comment 
have been dealt with already by the Webont WG, as noted previously.)

(2) You feel that the way that OWL was 'built on' RDFS is unsuitable 
or inappropriate in some way - in which case, it would help if you 
could sketch how you feel it would have been done better on a 
sublanguage, ie what you mean by 'built on' which is different from 
the relationship between OWL and RDF;

(3) What sense of 'can be deployed' makes OWL-DL not an illustration 
of how this is already  possible?

It would also help if you could say more exactly what you mean by a 
"FOL language". In my understanding, Lbase, CL and KIF are all FOL 
languages, but I take it that this does not satisfy you.

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Received on Thursday, 20 February 2003 14:24:20 UTC

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