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Re: pfps-12 lists are not well formed

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 18 Jun 2003 16:04:34 -0400 (EDT)
Message-Id: <20030618.160434.68451491.pfps@research.bell-labs.com>
To: danbri@w3.org
Cc: tolle@dbis.informatik.uni-frankfurt.de, bwm@hplb.hpl.hp.com, www-rdf-comments@w3.org

This appears to be on the right track, but I have no way of viewing the
other changes, and no way of viewing the changes in context, so I don't see
how I can determine whether the changes are satisfactory.

Peter F. Patel-Schneider
Bell Labs Research
Lucent Technologies



From: Dan Brickley <danbri@w3.org>
Subject: Re: pfps-12 lists are not well formed
Date: Wed, 18 Jun 2003 12:28:27 -0400

> resent copying Karsten, who also raised this issue. Karsten, could you 
> respond per the request below, letting us know if this is a satisfactory 
> resolution of your concern?
> 
> Thanks again for your comments on our work,
> 
> Dan
> 
> previous discussion:
> http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0422.html
> 
> * Dan Brickley <danbri@w3.org> [2003-06-18 12:16-0400]
> > 
> > * Peter F. Patel-Schneider <pfps@research.bell-labs.com> [2003-05-25 07:24-0400]
> > > 
> > > From: Brian McBride <bwm@hplb.hpl.hp.com>
> > > Subject: pfps-12 lists are not well formed
> > > Date: Sat, 24 May 2003 13:58:39 +0100
> > > 
> > > > Peter,
> > > > 
> > > > Danbri and I have been discussing how to resolve your issue about the 
> > > > wellformedness of lists:
> > > > 
> > > >    http://www.w3.org/2001/sw/RDFCore/20030123-issues/#pfps-12
> > > > 
> > > > We are proposing to add the following note to the text at:
> > > > 
> > > >    http://www.w3.org/TR/rdf-schema/#ch_collectionvocab
> > > > 
> > > > as the last paragraph.
> > > > 
> > > > [[
> > > > NOTE:  It is possible to construct RDF graphs that use the RDF collections 
> > > > vocabulary to partially describe a list.  Similarly there are graphs that 
> > > > use this vocabulary in a way that is consistent with the RDF(S) formal 
> > > > semantics, yet do not represent "well formed" lists.
> > > > ]]
> > > > 
> > > > We considered trying to trying to provide a full prose account of the 
> > > > wellformedness of lists, but are currently disinclined to attempt such an 
> > > > intricate task in natural language.
> > > > 
> > > > Will adding this note address your concern.  If not, could you please 
> > > > suggest alternative text that you would find more satisfactory.
> > > > 
> > > > Brian
> > > 
> > > I fail to see how this response addresses my comment.  
> > > 
> > > I don't see how it addresses
> > > 
> > > > The RDF Schema document provides intended meanings for some of the RDFS
> > > > vocabulary that is not supported by the RDF Semantics.  Vocabulary that
> > > > fits into this category includes rdfs:label and rdfs:comment.
> > > [from http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0126.html]
> > > 
> > > I don't see how it addresses
> > > 
> > > > Consider the following three examples (slightly reformatted but otherwise
> > > > unchanged):
> > > > 
> > > > 	rdf:type is an instance of rdf:Property that is used to state that
> > > > 	a resource is an instance of a class.  A triple of the form:
> > > > 		R rdf:type C
> > > > 	states that C is an instance of rdfs:Class and R is an instance of C.
> > > > 
> > > > 	rdf:first is an instance of rdf:Property that is used to indicate
> > > > 	the first item of a list.  A triple of the form:
> > > > 		L rdf:first O
> > > > 	states that L is an instance of rdf:List and that O is the first
> > > > 	item of the list. 
> > > > 
> > > > 	rdfs:label is an instance of rdf:Property that is used to provide a
> > > > 	human-readable version of a resource's name.  A triple of the form:
> > > > 		R rdfs:label L
> > > > 	states that L is a human readable label for R.
> > > > 
> > > > There is essentially no difference between the way these three are worded.
> > > > However, the first (rdf:type) is a fundamental part of the semantics of
> > > > RDF.  There are semantic conditions in RDF that make the description above
> > > > for rdf:type part of the very meaning of RDF.  The second (rdf:first) and
> > > > third (rdfs:label), on the other hand, have a very different status.  There
> > > > are no semantic conditions that force the descriptions above for these two
> > > > vocabulary elements to play the roles given for them.
> > > [from http://lists.w3.org/Archives/Public/www-rdf-comments/2003JanMar/0133.html]
> > > 
> > > The point of my comments here has always been that there are parts of the
> > > RDF Schema document that go beyond what is supported by the RDF semantics.
> > > I believe that these parts of the document should be changed, and that
> > > changes to other parts of the document will not suffice to override these
> > > over-reaching parts of the document.
> > > 
> > > For the case of rdf:first above, I would much prefer
> > > 
> > >  	rdf:first is an instance of rdf:Property that can be used to build
> > >  	descriptions of lists and other list-like structures.  A triple of
> > >  	the form:
> > >  		L rdf:first O
> > >  	states that there is a first-element relationship between L and O.
> > > 
> > > 	Note:  RDFS does not require that there be only one first element
> > > 	of a list-like structure, or even that a list-like structure have a
> > > 	first element.
> > 
> > This looks good. At the June 6th telecon[1] we decided to run with your 
> > proposed form of words, but note that your text didn't mention the 
> > domain and range constraints associated with these concepts.
> > 
> > A slightly amended form is:
> > [[
> > rdf:first is an instance of rdf:Property that can be used to
> > build descriptions of lists and other list-like structures.
> > A triple of the form:
> >   
> >   L rdf:first O
> >   
> > states that there is a first-element relationship between L and O.
> > The rdfs:domain of rdf:first is rdf:List.  The rdfs:range of rdf:first
> > is rdfs:Resource.
> >   
> > Note:  RDFS does not require that there be only one first element of
> > a list-like structure, or even that a list-like structure have a first
> > element.
> > ]]
> > 
> > 
> > > I note that similar changes would have to be make for at least rdf:rest and
> > > rdf:List.
> > 
> > Agreed.
> > 
> > The WG (per [1]) proposes to close this issue by resolving to adopt text in the 
> > above form for the RDF lists vocabulary.
> > 
> > Please reply to this message as to whether this response is
> > satisfactory, copying www-rdf-comments@w3.org. 
> > 
> > Dan
> > 
> > [1] http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2003Jun/0067.html
Received on Wednesday, 18 June 2003 16:06:58 GMT

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