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Re: semantics update

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Tue, 29 Jul 2003 08:00:39 -0400 (EDT)
Message-Id: <20030729.080039.125111913.pfps@research.bell-labs.com>
To: phayes@ihmc.us
Cc: w3c-rdfcore-wg@w3.org, www-rdf-comments@w3.org

From: pat hayes <phayes@ihmc.us>
Subject: semantics update
Date: Mon, 28 Jul 2003 23:29:18 -0500

> http://www.ihmc.us/users/phayes/RDF_Semant_Edit_Weak.html
> 
> now reflects the post-Beckett/PFPS/Carroll editing and all subsequent 
> decisions. It has a slightly different look/feel (colors, table 
> titles etc) , updated references (though if anyone has any complaints 
> about any of those please feel free to correct me) and some more 
> anchors and internal links. Ive made the text links slightly visible 
> by messing with the background color, but if people don't like this 
> its easy to tweak it in some other way.
> 
> Text changes since the last version are in red. They include 
> rewriting of the definition of 'merge', some minor rewordings to 
> clarify meanings more carefully, and putting back the definition of 
> 'vocabulary entailment' which had gotten lost somewhere (its now 
> section 2.1 and has several links to it) and references to blank node 
> *identifiers* in the statement of the rules (suggested by Dave). Also 
> the dire warning about rdf:value (section 3.2.4) has been made less 
> dire, also suggested by Dave.
> 
> Significant changes are that XMLiteral values are stated explicitly 
> to be distinct from character strings (defn of RDF interpretation, 
> section 3), and the equivalence between plain literals and xsd:string 
> typed literals is noted explicitly and an inference rule provided 
> (end of section 7.4). The wording of the Lbase translation has been 
> slightly altered to fit that last change also.
> 
> The change list has been rewritten and is at the end.
> 
> Pat
> 
> PS. Peter, I believe this now addresses all your concerns.

It may be that the changes do address all my concerns, I don't have time to
check just now, and may not for at least a week.


However, during the quick check I just made I found some remaining
concerns.  The first thing I checked was the list of post-last-call
changes.  I noticed that several changes that result in changes to RDF(S) 
entailments are not mentioned as substantial changes.

The change making LV = ICEXT(I(rdfs:Literal)) means that
	ex:foo ex:rel "a" .
rdfs-entails
	ex:foo ex:rel _:x .
	_:x rdf:type rdfs:Literal .
whereas it does not in the last call semantics.  This was pointed out in
http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0085.html. 

The change to datatyping in RDF makes many changes to D-entailments.  In
the last call semantics, there were few D-entailments, as there was no way
to impose connections between typed literals and datatypes.  For example,
	ex:foo ex:rel "1"^^xsd:decimal .
did not xsd-entail
	ex:foo ex:rel "01"^^xsd:decimal .
in the last call semantics because xsd-interpretations did not require that
I(xsd:decimal) be the xsd:decimal datatype.

The change requiring non-emtpy datatypes, although it technically does not
affect any entailments, changes the permissable set of RDF datatypes, and
thus forms a significant change to the RDF datatyping design.

Without a comprehensive list of such changes, I do not view the RDF
Semantics document as complete.


Problems arise in the description of other changes.  I can't
imagine how the significant changes to the mapping to Lbase can be listed
under ``The following changes do not effect [sic] the technical content.''

The change to lists doesn't affect any entailments that I can see.  In
fact, the it doesn't change anything at all with respect to the semantics,
even the set of RDF graphs that are the result of RDF/XML parsing.

The change to datatypes is not needed for compatability with OWL.  It is
instead needed because the last-call treatment of datatypes didn't work
right. 


Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies


PS:  I also noticed a typo in 4.3 -  Rdf -> Rdfs
Received on Tuesday, 29 July 2003 08:00:48 EDT

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