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Re: [SKOS] "SKOS RDF schema"

From: Sean Bechhofer <sean.bechhofer@manchester.ac.uk>
Date: Thu, 14 May 2009 17:24:53 +0100
Message-Id: <2D28B359-D384-491F-84AD-77141643066A@manchester.ac.uk>
Cc: Alistair Miles <alimanfoo@googlemail.com>, Antoine Isaac <aisaac@few.vu.nl>, SWD Working Group <public-swd-wg@w3.org>
To: Thomas Baker <tbaker@tbaker.de>

On 13 May 2009, at 20:00, Thomas Baker wrote:

> On Wed, May 13, 2009 at 05:15:44PM +0100, Alistair Miles wrote:
>> I'm looking forward to a proposal from Tom on the way forward  
>> here. In
>> the recent editors' draft I published at [1], I did not make any
>> changes to the language on conformance or normativity from the CR
>> version.
> ...
>> I suggest keeping section 1.8 as it is, but adding some prose to
>> appendix C along the lines of what Tom is suggesting for the  
>> namespace
>> documents.
>
> Dear all,
>
> My posting about SKOS namespace documents on 6 May [1]
> overlooked some good suggestions from Alistair on 16 April [2].
> I have exchanged some mail about this with Alistair.
>
> Taking Alistair's suggestions and document titles into account,
> and drawing on text from Sean's draft [3], here is the proposal:
>
> -- Text on "SKOS Namespace Documents" along the following lines:
>
>    Following Architecture of the World Wide Web, Volume One,
>    a "namespace document" is an "information resource
>    that contains useful information, machine-usable and/or
>    human-usable, about terms in the namespace" [*].
>
>    The SKOS vocabulary is a conceptual resource identified
>    by the namespace URI http://www.w3.org/2004/02/skos/core#.
>    The normative definition of the SKOS vocabulary is found
>    in SKOS Reference (this document).
>
>    The following namespace documents provide alternative
>    representations of the SKOS vocabulary:
>
>    a. SKOS Namespace Document - HTML Variant (normative)
>
>       The SKOS vocabulary is summarized in this HTML document,
>       which is served via content negotiation using Recipe 3 of
>       "Best Practice Recipes for Publishing Vocabularies"
>       [RDF-RECIPES].  Clients requiring HTML or XHTML should
>       include an appropriate "Accept" header in the HTTP
>       request.  This document replicates an Appendix of
>       SKOS Reference [SKOS-REFERENCE].
>
>    b. SKOS Namespace Document - RDF/XML Variant (normative)
>
>       This RDF schema document expresses the SKOS vocabulary [or
>       do we need to say data model here?], in so far as
>       possible, as RDF triples.  It is served via content
>       negotiation using Recipe 3 of "Best Practice Recipes for
>       Publishing Vocabularies" [RDF-RECIPES].  Clients requiring
>       RDF/XML should include an appropriate "Accept" header in
>       the HTTP request.  Alternatively, the RDF schema can be
>       referenced directly (and downloaded) by citing its URI.
>
>       It is not possible to express all of the statements of the
>       SKOS data model as RDF triples, so this schema forms a
>       normative subset of SKOS Reference.  The RDF schema
>       defines an OWL Full ontology [OWL-SEMANTICS]
>       [OWL-REFERENCE].  SKOS vocabularies can be defined as
>       instances of this ontology.
>
>    c. SKOS RDF Schema - OWL 1 DL Sub-set (informative)
>
>       For the convenience of tools and applications that wish to
>       work within the constraints of OWL DL, this document
>       provides a modified, informative, schema which conforms to
>       those constraints.  Note that this schema is obtained
>       through the deletion of triples representing axioms that
>       violate OWL DL constraints.  Alternative prunings could be
>       performed.
>
> -- Document a. SKOS Namespace Document - HTML Variant
>    -- URL like http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/ 
> skos.html
>    -- Simple text is limited to:
>
>       The following table gives a non-normative overview of the
>       SKOS vocabulary; it replicates a table found in the
>       (normative) SKOS Reference [SKOS-REFERENCE].  This
>       document can be referenced directly, by its own URI
>       [CITE], or indirectly, by content negotiation from the
>       SKOS namespace URI [CITE] as described in Appendix C of
>       SKOS Reference [SKOS-REFERENCE].
>
> -- Document b. SKOS Namespace Document - RDF/XML Variant
>    -- URL like http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/ 
> skos.rdf
>    -- No text, but seeAlso SKOS-REFERENCE.
>
> -- Document c. SKOS RDF Schema - OWL 1 DL Sub-set (informative)
>    -- URL like http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/ 
> skos-owl1-dl.rdf
>    -- No text, but seeAlso SKOS-REFERENCE.
>
> -- Discuss namespace documents for XL in the Appendix about XL [5].
>
> Then:
>
> -- Disable multiviews for the "generic document" [*] as it may 
>    cause confusion.
>    [*] http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos
>
> -- Implement recipe 3 redirects from <http://www.w3.org/2004/02/ 
> skos/core>
>    ("SKOS Vocabulary Namespace URI") to [a] and [b].
>
> -- As suggested by Alistair, redirect from
>    <http://www.w3.org/2004/02/skos/core.rdf> ("Latest SKOS
>    Namespace Document RDF/XML Variant") to [b] as a convenient
>    shortcut for developers, mentioned on the SKOS web site but not
>    otherwise included in formal documentation.
>
> In other words, I agree with Alistair that the HTML
> representation [3] should be called "SKOS Namespace Document -
> HTML Variant" (instead of "SKOS Namespace Documentation").
>
> I would prefer to see this explanatory text about "namespace
> documents" moved to the appendix of SKOS Reference (Alistair's
> "adding some prose to appendix C along the lines of what Tom is
> suggesting for the namespace documents").  I see some overlap
> between the proposed appendix and the current Appendix C "SKOS
> Data Model as RDF Triples" [4], which could perhaps be renamed
> Appendix C "SKOS Namespace Documents".
>
> This proposal largely follows Alistair's suggestions [2] but
> diverges from them inasmuch Alistair was assuming that the HTML
> variant would link directly to the RDF/XML variant and the OWL
> DL prune.  I am suggesting here that each of the three namespace
> documents (a,b,c) contain minimal text and point back to SKOS
> Reference, where the overview of representations and content
> negotiation would be presented; SKOS Reference should point to
> each of the namespace documents.
>
> If the introduction of this much explanatory text into an
> Appendix of SKOS Reference itself is too big a change at this
> stage in the process, I could live with putting all of the
> explanatory text above into the HTML variant as an Introduction.
> However, it seems more elegant to put this important material
> into the main SKOS Reference document and keep the namespace
> representations as simple as possible.
>
> Tom
>
> [1] http://lists.w3.org/Archives/Public/public-swd-wg/2009May/ 
> 0032.html
> [2] http://lists.w3.org/Archives/Public/public-swd-wg/2009Apr/ 
> 0043.html
> [3] http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/skos.html
> [4] http://www.w3.org/TR/skos-reference/#triples
> [5] http://www.w3.org/TR/skos-reference/#L5212

I am happy with Tom's proposed changes (and agree with his claim of  
elegance/simplicity). I have taken a "pre-emptive strike" as I had  
some available time and made some changes to the working copies at  
[1,2,3,4,5] -- these changes can, of course be rolled back via cvs if  
necessary. Changes made:

1/ Altered Appendix C of [1] along the lines proposed above
2/ Removal of text from skos.html [2]
3/ Addition of rdfs:seeAlso links to [3,4]

Implementation of multiviews, redirects etc is for someone else :-)

Couple of issues I still see:

A/ The handling of XL is slightly inconsistent. I've added an XL HTML  
variant [5] (which was present in earlier versions, but has been  
edited to fit the model described above). There is no corresponding  
table in Reference though. How do we handle the discussion of the XL  
namespace documents? Again, it seems a little inconsistent to have an  
Appendix discussing this for SKOS and a section of an appendix  
describing it for XL.

But I'm not *that* bothered at this point....

B/ Is there a URI for the DL prune?

Cheers,

	Sean

[1] http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/
[2] http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/skos.html
[3] http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/skos.rdf
[4] http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/skos-dl.rdf
[5] http://www.w3.org/2006/07/SWD/SKOS/reference/20090315/skos-xl.html

--
Sean Bechhofer
School of Computer Science
University of Manchester
sean.bechhofer@manchester.ac.uk
http://www.cs.manchester.ac.uk/people/bechhofer
Received on Thursday, 14 May 2009 16:23:03 UTC

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