comments on proposed agenda items

From: Peter F. Patel-Schneider (
Date: 10/01/01

Here are my promised points on the proposed agenda items: 

1/ Comments about the model theory itself, as it relates to RDF and RDF
   Schema, that we may want to get back to the RDF Core WG.

a/ This was a very good job by Pat, even with the mostly minor points that
   I brought out last week.

b/ The only remaining major point that I have is that the model theory
   commits RDF to a particular view of how literals obtain meaning.  [See
   below as well.]  In this view the complete meaning of a literals is
   obtained by its lexical form, which means:
   i) the same lexical form, i.e., 010, has to have the same meaning
   everywhere, i.e., can't be a string sometimes and an integer otherwise;
   ii) the meaning of a literal cannot be (partially) defined by domain and
   range constraints.

2/ Discussion of the impact of the model theory on DAML+OIL.

a/ The non-literal part of the model theory seems to me to fit very well
   with what we need for DAML+OIL.  In partcular, I have modified the model 
   theory for DAML+OIL to fit with the RDF model theory.  (See my messages
   over the weekend.)  In my view, this enhances DAML+OIL, and provides an
   interesting new direction for work on description logics, that of
   allowing a weak theory of types into the object language without messing
   up the rest of the description logic theory.  (At least I hope so.  I
   haven't completely thought out the consequences of this approach.)  I
   would like to get more description logic theoreticians involved in this.

b/ The literal part of the model theory is quite restrictive.  It does not
   allow the meaning of a literal to be determined by RDF-supplied typing.
   I view this as a serious, possibly fatal, flaw, particularly with
   respect to DAML+OIL.

3/ Discussion of the political aspects of the situation with respect to the
   RDF Core WG, the WebOnt WG, W3C, and the Joint Committee.

a/ I strongly feel that the delay in the formation of the WebOnt WG is
   hurting RDF efforts, as there is no formal mechanism for the concerns of
   the Joint Committee to get to the RDF Core WG, nor is there a good
   mechanism for information from the RDF Core WG to get to the Joint

b/ In my view, the RDF Core WG is only hurting itself and RDF by moving
   further from XML Schema standards with respect to literals.  Again in
   my view, they should be exploring mechanisms for bringing RDF literals
   in line with XML Schema datatypes, and not inventing a new, complex


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