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Re: pfps-12 lists are not well formed

From: Dan Brickley <danbri@w3.org>
Date: Wed, 18 Jun 2003 12:16:07 -0400
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: bwm@hplb.hpl.hp.com, www-rdf-comments@w3.org
Message-ID: <20030618161607.GJ11302@tux.w3.org>

* 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 12:16:14 GMT

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