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Re: substantive semantics change?

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Wed, 12 Nov 2003 21:17:26 +0100
To: w3c-rdfcore-wg@w3.org
Message-Id: <200311122117.26265.jjc@hpl.hp.com>


All three tests hold on LC2, and LC1 and the September draft as far as I can 
tell now, and also the latest editors draft. The proof hinges on an error in 
the wording of the LC1 draft which was fixed about July in the editors draft 
but then got changed again by September - I've really no idea why.


I now think the thought that all these entailments held, even on LC1, even
the harder one.

e.g.

*empty*

rdfs-entails

_:a rdf:type rdfs:ContainerMemebershipProperty .


Proof (using text which is only editorially changed since LC1)

Take an RDFS interpretation I of *empty*, since
[[
An rdfs-interpretation of V is an rdf-interpretation I of (V union rdfV union
rdfsV) which satisfies the following semantic conditions and all the triples
in the subsequent table, which we will call axiomatic triples.
]]

(note rdfV and rdfsV are finite in LC1, but the axiomatic triples is an 
infinite set).

From the axiomatic triples we have

I(rdf:_1 rdf:type rdfs:ContainerMembershipProperty) = true

and then we trivially get

rdf_:a rdf:type rdfs:ContainerMembershipProperty) = true

Hence, I think this change is one we merely conjecture as substantive.
The motivation for the change is that the LC2 entailment might not be 
transitive. The PC candidate entailment is transitive. Hence if the 
motivation is valid the two entailments cannot be the same and the change is 
substantive. If the change is editorial then it is unmotivated.

I doubt the process document discusses changes that are thought to be 
substantive, but might merely be editorial.

I regret that at the point the semantics doc changed to (intending to) have an 
infinite closure of ground terms we were not alerted to this substantive 
change. I believe I would have opposed. However, it seems to have been a 
while ago, and not something that happened on Friday.

Jeremy
Received on Wednesday, 12 November 2003 15:17:58 EST

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