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Re: On equivalence of tidy/untidy (was: Re: Reopening tidy/untidy decision)

From: Jos De_Roo <jos.deroo.jd@belgium.agfa.com>
Date: Tue, 1 Oct 2002 22:46:36 +0200
To: "Graham Klyne <Graham.Klyne" <Graham.Klyne@MIMEsweeper.com>
Cc: Sergey Melnik <melnik@db.stanford.edu>, w3c-rdfcore-wg@w3.org, w3c-rdfcore-wg-request@w3.org
Message-ID: <OFA7855917.3199D719-ONC1256C45.0071F75C-C1256C45.00722198@agfa.be>


Graham, I agree with your message
(as well as the former one)

 -- ,
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/


                                                                                                                         
                    Graham Klyne                                                                                         
                    <Graham.Klyne@MIMEsw       To:     Sergey Melnik <melnik@db.stanford.edu>                            
                    eeper.com>                 cc:     w3c-rdfcore-wg@w3.org                                             
                    Sent by:                   Subject:     Re: On equivalence of tidy/untidy (was: Re: Reopening        
                    w3c-rdfcore-wg-reque        tidy/untidy decision)                                                    
                    st@w3.org                                                                                            
                                                                                                                         
                                                                                                                         
                    2002-10-01 05:48 PM                                                                                  
                                                                                                                         
                                                                                                                         





At 10:24 AM 10/1/02 +0200, Sergey Melnik wrote:
>Our problem is that the entailment capability is *not* part of RDF
>spec.    If it were, then we could define formally what the result of
>entailment should be, applied to graphs. However, we do not require each
>and every RDF application to support entailment (thanks God).

Entailment *capability* may not be part of the RDF spec, but certain
allowable entailments *are*.  The fact that RDF permits certain entailments

is not the same as saying RDF requires applications to deliver those
entailments.

>Recall that entailment is a syntactic procedure, more precisely, a binary
>relation that holds between syntactic sentences (graphs, in our case).

?!?  I thought entailment was precisely a *semantic* relation, defined in
terms of truth of expressions (graphs) (which I grant are syntactic
entities) under any interpretation.

>Defining entailment (in terms of logical inference) is comparable to
>defining the semantics of a query language, like SQL. At this point of
>time, we do not force every RDF application to support a specific query
>language (which we could use to test tidiness)...

"Defining entailment (in terms of logical inference)" sounds line an
oxymoron to me.

But I agree that we don't require all applications to find all valid
entailments.

In fact, I don't think we require applications to do anything (though it is

sometimes convenient to describe aspects of RDF by characterizing our
expectations of applications -- I thought the whole idea of the formal
semantics was to be able to nail down RDF meaning without having to
describe applications).

#g


-------------------
Graham Klyne
<GK@NineByNine.org>
Received on Tuesday, 1 October 2002 16:57:34 EDT

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