Re: Vocabulary (ontology) URI vs namespace

Michael

I must say I am quite puzzled by the VoID recommendations you point at, and
of which I was not aware so far I must admit (homework to do).
Following this recommendation, you would declare in the example 1 (c4o)
that the vocabulary URI is http://purl.org/spar/c4o/
although the said vocabulary declares itself explicitly its URI to be
http://purl.org/spar/c4o

The VoID recommendation might be OK for a vocabulary which does not declare
explicitly its URI, but if it does, VoID should recommend, if you ask me,
to use the URI as declared by the vocabulary owner (which the editor of the
VoID declaration should be able to find out).

Bernard

PS : I've an interesting answer from Stuart Williams regarding this
question, explaining two viewpoints, one making distinct the ontology as an
abstract Work (to use FRBR parlance) and the ontology document (Expression
or maybe Manifestation in FRBR). Our take at LOV on this issue has been
expressed in
http://blog.hubjects.com/2012/07/frbr-in-lov-vocabulary-is-work.html


2012/8/31 Michael Hausenblas <michael.hausenblas@deri.org>

> Bernard,
>
> Great and useful work, thanks!
>
> > So my question is : should the practice of examples 1 and 2 be
> recommended as the best one, namely :
>
> My 2c (from the VoID spec):
>
> http://www.w3.org/TR/void/#vocabularies
>
> Cheers,
>            Michael
>
> --
> Dr. Michael Hausenblas, Research Fellow
> DERI - Digital Enterprise Research Institute
> NUIG - National University of Ireland, Galway
> Ireland, Europe
> Tel.: +353 91 495730
> http://mhausenblas.info/
>
> On 31 Aug 2012, at 12:19, Bernard Vatant wrote:
>
> > Hello all
> >
> > Having harvested as of today 280 vocabularies/ontologies at
> http://lov.okfn.org/dataset/lov
> > We have stumbled on all possible (I think) configurations regarding
> vocabulary URI (or IRI) and namespace, and it's sometimes driving me nuts :)
> >
> > A common (best?) practice is to declare the vocabulary URI as a base URI
> without any trailing # or /, to make it distinct from the ontology
> namespace.
> >
> > Example 1 : c4o
> >
> > URI : http://purl.org/spar/c4o
> > namespace : http://purl.org/spar/c4o/
> >
> > Example 2 : c4n
> >
> > URI : http://vocab.deri.ie/c4n
> > namespace : http://vocab.deri.ie/c4n#
> >
> > In both cases the vocabulary URI is declared formally using owl:Ontology.
> >
> > In both cases the root URI and the namespace resolve and conneg nicely.
> >
> > In the second example the namespace is formally declared using
> vann:preferredNamespaceUri, which is nice to have
> >
> > There are also many cases where the namespace is used more or less
> explicitly as the vocabulary URI.
> >
> > Example 4 : dcterms
> >
> > Both http://purl.org/dc/terms/ and http://purl.org/dc/terms currently
> resolve to http://dublincore.org/2012/06/14/dcterms.rdf where one can
> find :
> >
> > <rdf:Description rdf:about="http://purl.org/dc/terms/"> etc
> > although this is not a owl:Ontology declaration, this implicitly
> indicates http://purl.org/dc/terms/ as the URI of the vocabulary.(would
> be better if explicit ...)
> >
> > Using purl, it's often the case that the root URI does not even resolve.
> >
> > Example 4 : af
> >
> > The namespace URI : http://purl.org/ontology/af/
> >
> > ... redirects to http://motools.sourceforge.net/doc/audio_features.rdf
> >
> > ... where one can read
> > <owl:Ontology
> rdf:about="file:///home/moustaki/work/workspace/motools/af/rdf/audio_features.n3">
> >
> > whereas http://purl.org/ontology/af is 404
> >
> > This example is a bit extreme (apologies to Yves for pointing that
> publicly) but we have all sorts of in-between, such as no owl:Ontology
> declaration at all, or lazy owl:Ontology rdf:about=""  combined with
> redirection so it's to everyone guess what to put in the "" ...
> >
> > So my question is : should the practice of examples 1 and 2 be
> recommended as the best one, namely :
> >
> > - Use a root URI (without either trailing # or / or file extension) as
> the vocabulary URI
> > - Declare it formally using a owl:Ontology declaration in the RDF, and
> explicitly in the HTML documentation
> > - Make this root URI resolve to both vocabulary file and documentation
> using proper content negociation
> >
> > Plus (nice to have)
> >
> > - Declare explicitly the vocabulary namespace URI (either / or #) using
> vann:preferredNamespaceUri (not only xmlns)
> > - Have the namespace resolve to the root URI
> >
> > Thanks for comments !
> >
> > Bernard
> >
> > --
> > Bernard Vatant
> > Vocabularies & Data Engineering
> > Tel :  + 33 (0)9 71 48 84 59
> > Skype : bernard.vatant
> > Blog : the wheel and the hub
> >
> > --------------------------------------------------------
> > Mondeca
> > 3 cité Nollez 75018 Paris, France
> > www.mondeca.com
> > Follow us on Twitter : @mondecanews
> >
>
>


-- 
*Bernard Vatant
*
Vocabularies & Data Engineering
Tel :  + 33 (0)9 71 48 84 59
Skype : bernard.vatant
Blog : the wheel and the hub <http://blog.hubjects.com/>

--------------------------------------------------------
*Mondeca**          **                   *
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www.mondeca.com
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