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Re: Proposal to resolve ISSUE-102 (well-formed lists)

From: Richard Cyganiak <richard@cyganiak.de>
Date: Fri, 9 Nov 2012 11:26:38 +0000
Cc: RDF Working Group WG <public-rdf-wg@w3.org>
Message-Id: <D2D4233C-849A-42E4-BDA7-014181415FC1@cyganiak.de>
To: Dan Brickley <danbri@danbri.org>
Dan,

You're a master of vagueness. Are these your concerns?

1. You believe that RDFS should avoid any kind of conformance statements, including RECOMMEND-level statements on the use RDFS terms.

2. You are concerned that the proposal is not phrased as actual literal spec text. Thus is does not yet spell out all the details that would enable you, as the editor of the spec, to assess whether the text is appropriate for the spec.

3. You believe that “graph containing no malformed lists” is a more useful concept than “graph consisting only of one well-formed list”.

Best,
Richard



On 9 Nov 2012, at 09:23, Dan Brickley wrote:

> On 9 November 2012 08:48, Richard Cyganiak <richard@cyganiak.de> wrote:
>> ISSUE-102: Shall we highlight Turtle's list structures as "Well-Formed Lists" in one of our Recs?
>> http://www.w3.org/2011/rdf-wg/track/issues/102
>> 
>> 
>> PROPOSAL: Define the concept “well-formed list” in detail in RDF Schema, including a nice diagram. State that any use of terms from the collections vocabulary SHOULD be part of a well-formed list. Update Semantics to remove discussion of collections in 3.3.3. Update Turtle and RDF/XML to refer to well-formed lists when introducing the respective syntax shorthands. Send an email to OWL WG comments list informing them of this and suggest that future versions of OWL do the same.
> 
> re http://www.w3.org/TR/rdf-schema/#ch_collectionvocab
> 
> Use of the word 'SHOULD' somewhat frightens me, as it moves RDFS into
> a very different role. Historically, we have limited ourselves to a
> kind of passive, declarative specification, defining the meaning of
> terms.
> 
> When SHOULD enters, we need to be very clear who we are shouting at,
> and why. Is it an error to take a set of triples (a graph) and produce
> a subset? Many of us do that all the time, using a variety of tools
> (including APIs, grep, ...). Is it an error to share the results?
> Privately? In small groups? Whose error is it if someone SPARQLs with
> '?x rdf:first ?y' and pulls out just pieces of a list through a query
> API? Or does something with sameAs to fold the list back on itself? If
> our notion of error is grounded in patterns of truth, I think we have
> the machinery. But this notion of 'SHOULD' seems more in a software
> engineering mode.
> 
> What underlying concepts are needed for us to "State that any use of
> terms from the collections vocabulary SHOULD be part of a well-formed
> list" ? Does this rely on the notion of a "graph" in some sense? As we
> saying that no graphs ought to exist whose use of
> List/first/rest/next/nil violates some set of constraints. Is there
> candidate text around somewhere for 'well-formed list'? I don't think
> a picture will capture the subtleties. Must the elements of the list
> be described with only bNodes? Can they have for example functional
> properties that imply identity between list elements? (under which OWL
> semantics).
> 
> A more declarative flavour of this would be to say there are two kinds
> of RDF graph. Those that use rdf:List in certain troublesome patterns,
> and those that don't. But how do those details look? What would an
> rdf:GraphThatHasDodgyLookingLists definition look like? Can it be
> expressed in SPARQL 1.1, partially or in entirety?
> 
> Dan
> 
Received on Friday, 9 November 2012 11:27:20 GMT

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