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Re: semantics update

From: pat hayes <phayes@ihmc.us>
Date: Wed, 30 Jul 2003 01:24:15 -0500
Message-Id: <p06001a50bb4d0ce373f7@[10.0.100.23]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
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.

I view both of these as ERRORS in the last call document which have 
now been fixed, in both cases in close consultation with you, for 
which I am grateful.  So I am not sure what your point is here. Are 
you saying that you want us to revert to the situation in the LC doc?

>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.

Do you , honestly now, think of this as a SIGNIFICANT change? Can you 
cite any example that has been seriously proposed of a datatype with 
empty domains? Again, I regard the omission of this condition simply 
as an editorial oversight: frankly, I never even thought about the 
possibility of an empty dataype until you pointed out that it was not 
explicitly prohibited and, if ever defined, would produce strange 
behavior in the semantics. So I prohibited it.

>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.''

Perhaps that could be better phrased. I should have said 'normative 
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.

That is true, I should have listed that in the previous section.

>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.


It was the need to support OWL identity reasoning which brought this 
to the fore, but OK.

>
>Peter F. Patel-Schneider
>Bell Labs Research
>Lucent Technologies
>
>
>PS:  I also noticed a typo in 4.3 -  Rdf -> Rdfs

thanks.

OK, the version at my URI now has the change list rephrased more in 
line with your remarks above (and the typo fixed). Textual changes 
marked in red; some of the material has been moved to other headings 
also. Apart from the typo, the main text is unaltered.

Pat


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Received on Wednesday, 30 July 2003 02:24:18 EDT

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