Re: [SKOS] "SKOS RDF schema"

hi tom,

i'd be happy with the following setup for PR, based on sticking close
to established practice e.g. OWL and on making the least change to our
own practices so far, although i'm happy to consider alternatives if
anyone has a better idea...


== SKOS ==

we publish a "SKOS Namespace Document HTML Variant", at a url like:

[a] http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos.html

we publish a "SKOS Namespace Document RDF/XML Variant", at a url like:

[b] http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos.rdf

we publish a "SKOS RDF Schema (OWL 1 DL Sub-set)" at a url like:

[c] http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos-owl1-dl.rdf
 
we make sure [a] has links directly to [b] and [c].

in an appendix to the SKOS Reference, we state that the document at
[b] should be considered to be a part of the SKOS Reference, and hence
a part of the Recommendation. the appendix also states that [b] is a
normative subset of the SKOS data model.

in a separate appendix, we do the same for [c] (i.e. state that it is
a part of the Recommendation, and that it is a normative subset of the
SKOS data model).

we *do not* include the rdf/xml content of [b] or [c] explicitly in
these appendices, unless absolutely necessary to confer recommendation
status to the rdf/xml content. (it seems a bit crazy to do what owl 1
did and include the content of [b] or [c] explicitly in appendices to
the skos reference, and hence duplicate the rdf/xml content in two
places ... although if this is the only way we could resolve the
status issue, i could live with it.)

we do recipe 3 redirects from <http://www.w3.org/2004/02/skos/core>
("SKOS Vocabulary Namespace URI") to [a] and [b].

we redirect from <http://www.w3.org/2004/02/skos/core.rdf> ("Latest
SKOS Namespace Document RDF/XML Variant") to [b]. this link is just a
convenience shortcut for developers, we mention it on the SKOS web
site but we otherwise don't include it in formal documentation.

because of the way that [a] and [b] are published on an apache server
with multiviews enabled, there is also another url:

<http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos>

which is effectively a "generic document", but this is accidental and
not by design. If we need to refer to this in discussion, we could
call it the "SKOS Generic Namespace Document", but it is probably
better not to mention this link anywhere either in formal
documentation or on the web site, as it may cause confusion.

alternatively, we disable multiviews for the entire directory, and so
the URI above will 404. this might be safer, and would certainly avoid
confusion over what cool URI pattern we're doing.

a second alternative would be to switch from doing recipe 3 redirects
to doing 303 redirects to one generic document (see
<http://www.w3.org/TR/cooluris/#r303gendocument>), but it's a bit late
in the game to switch our practices like this, and would require some
testing and a rethink of inter-document links.


== 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.

because of the way that [d] and [e] are published on an apache server
with multiviews enabled, there is also another url:

<http://www.w3.org/TR/2009/PR-skos-reference-2009XXXX/skos-xl>

which is effectively a "generic document", but this is accidental and
not by design. If we need to refer to this in discussion, we could
call it the "SKOS XL Generic Namespace Document", but it is probably
better not to mention this link anywhere either in formal
documentation or on the web site, as it may cause confusion.

alternatively, we disable multiviews for the entire directory, and so
the URI above will 404.

...

how does that all sound?

tom suggests combining SKOS and SKOS XL namespace documents into a
single document, but i would rather keep them separate, mainly because
having them separate reinforces the fact that XL is an optional
extension to SKOS, and means that people coming first to SKOS don't
have to deal initially with the extra layer of complexity.

cheers,

alistair



On Mon, Apr 06, 2009 at 07:34:33PM +0200, Thomas Baker wrote:
> Dear all,
> 
> I'm looking at [1], also known as [2].
> 
> [1] http://www.w3.org/TR/2009/CR-skos-reference-20090317/skos.html
> [2] http://www.w3.org/TR/2009/CR-skos-reference-20090317/skos
> 
> This document calls itself "SKOS Simple Knowledge
> Organization System RDF Schema". 
> 
> One obvious problem is that the document is clearly an HTML
> page and not an RDF schema. It may seem obvious to us that it
> is really _about_ the RDF schema, but I can well imagine this
> causing some confusion.
> 
> In the section of that document labeled "SKOS RDF Schema", then,
> there is a link labeled "SKOS RDF Schema" which points to
> 
> [3] http://www.w3.org/2004/02/skos/core
> 
> which however -- since I am reading it in a browser --
> content-negotiates back to [1]! 
> 
> However, the section does provide an additional link directly
> to the schema itself ("download the RDF schema without content
> negotiation") [4].
> 
> [4] http://www.w3.org/2004/02/skos/core.rdf
> 
> Given the title and introduction, then, the reader does not
> necessarily expect to find the _contents_ of the RDF schema by
> scrolling down one screen.
> 
> I find this all delightfully confusing... :-)
> 
> Some issues and suggestions for discussion:
> 
> -- Maybe call the Web document [1-2] "Contents of the RDF 
>    schema for Simple Knowledge Organization System (SKOS)" 
>    or "Expressing SKOS in RDF" - in effect, anything but
>    "SKOS RDF schema" :-)
> 
> -- There should be a link labeled "SKOS RDF schema", but it 
>    should link to [4] directly, not via content negotiation from
>    [3].  The surrounding text, however, should describe the 
>    content negotiation mechanism clearly.
> 
> -- Status of the document [1-2]: I'm not sure we have properly
>    resolved this question. I think it would help the reader if
>    this document describes itself as a readable ready-reference
>    page which excerpts the contents of the RDF schema for SKOS,
>    and that the RDF schema for SKOS is itself a formalisation
>    of a subset of the semantic conditions described in SKOS
>    Reference, and that the SKOS Reference has the status of W3C
>    [Candidate] Recommendation.
> 
>    Like the OWL ontology [5], the RDF schema for SKOS does not
>    assert any status for itself, though in the case of OWL,
>    the contents of the schema are replicated in an appendix to
>    the Recommendation document [6], arguably conferring on the
>    schema itself a status of Recommendation, assuming it merely
>    replicates the text in the appendix.
> 
>    [5] http://www.w3.org/2002/07/owl
>    [6] http://www.w3.org/TR/owl-ref/#appB
> 
>    This text provides an opportunity to clarify that the SKOS
>    Reference is the [Candidate] Recommendation and that [1],
>    [2], and [4] are all excerpts of that Recommendation.
>    (The text should point out that it is not possible to
>    express all of the statements of the SKOS data model as RDF
>    triples and thus the schema forms a "normative subset" of the
>    specification.)
> 
> -- I'm wondering if this document [1-2] might be a good 
>    place to introduce and link any DL versions of SKOS as per Sean's
>    discussion in [7].  The document could briefly explain the need 
>    to have a DL ontology in some contexts, describe the algorithm
>    by which some of the axioms in [4] are "thrown away" (or filtered
>    out).  In a way, the DL schema is arguably just another subset
>    of the semantic conditions described SKOS Reference, albeit a 
>    deliberately lossy one.  Grouping points to the RDF, HTML, and DL 
>    excerpts together in one document would be helpful; and where else 
>    to do that but in this document [1-2]?  (This assumes we want to 
>    publish, or indeed say anything at all about, a DL version - also an
>    issue for discussion.)
> 
>    [7] http://lists.w3.org/Archives/Public/public-swd-wg/2009Mar/0071.html
> 
> -- The HTML representation [1-2] should include labels.
> 
> -- If scripts were used to extract [1-2] from SKOS Reference and to 
>    generate the DL version, it might be useful to point to those scripts
>    or include them in an appendix.
> 
> -- Instead of replicating this construct separately for the XL namespace [8], 
>    maybe SKOS and SKOS-XL could be usefully combined into one document
>    "Expressions of SKOS Reference in RDF" (since SKOS Reference defines both
>    the SKOS and XL namespaces).  Such a title would make clear that it 
>    derives from SKOS Reference without implying that the document is itself
>    an RDF schema.
> 
>    [8] http://www.w3.org/2006/07/SWD/SKOS/reference/20081001/skos-xl.html
> 
> If the document [1-2] were to do all of the above, might we
> not want to formally approve it as a Working Group Note? That
> would remove any confusion or ambiguity as to its status.  I 
> hesitate because I'm not sure now under what circumstances a 
> reader would normally click on or be redirected to this document
> and whether, in those contexts, the reader might find it confusing
> to encounter something with the status of Note.
> 
> Tom
> 
> -- 
> Tom Baker <tbaker@tbaker.de>
> 

-- 
Alistair Miles
Senior Computing Officer
Image Bioinformatics Research Group
Department of Zoology
The Tinbergen Building
University of Oxford
South Parks Road
Oxford
OX1 3PS
United Kingdom
Web: http://purl.org/net/aliman
Email: alistair.miles@zoo.ox.ac.uk
Tel: +44 (0)1865 281993

Received on Tuesday, 14 April 2009 10:06:43 UTC