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Re: [SKOS] "SKOS RDF schema"

From: Thomas Baker <tbaker@tbaker.de>
Date: Wed, 13 May 2009 21:00:01 +0200
To: Alistair Miles <alimanfoo@googlemail.com>
Cc: Antoine Isaac <aisaac@few.vu.nl>, SWD Working Group <public-swd-wg@w3.org>
Message-ID: <20090513190001.GB2408@octavius>
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

> == SKOS XL ==
> 
> we publish a "SKOS XL Namespace Document HTML Variant", at a url like:
> 
> [d] http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos-xl.html
> 
> we publish a "SKOS XL Namespace Document RDF/XML Variant", at a url like:
> 
> [e] http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos-xl.rdf
> 
> we publish a "SKOS XL RDF Schema (OWL 1 DL Sub-set)" at a url like:
> 
> [f] http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos-xl-owl1-dl.rdf
> 
> which imports [c] instead of <http://www.w3.org/2004/02/skos/core> but
> is otherwise the same as [e].
> 
> we make sure [d] links directly to [e] and [f].
> 
> in an appendix to the SKOS Reference, we state that the document at
> [e] should be considered to be a part of the SKOS Reference, and hence
> a part of the Recommendation. in a separate appendix, we do the same
> for [f]. we *do not* include the rdf/xml content of [e] or [f]
> explicitly in these appendices.
> 
> we do recipe 3 redirects from <http://www.w3.org/2008/05/skos-xl>
> ("SKOS XL Vocabulary Namespace URI") to [d] and [e].
> 
> we redirect from <http://www.w3.org/2008/05/skos-xl.rdf> ("Latest
> SKOS XL Namespace Document RDF/XML Variant") to [b]. this link is just a
> convenience for developers, we mention it on the SKOS web site but we
> otherwise don't include it in formal documentation.

-- 
Tom Baker <tbaker@tbaker.de>
Received on Wednesday, 13 May 2009 19:00:49 UTC

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