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Re: FW: [SKOS] inScheme and rdfs:isDefinedBy (cf. ISSUE-36 ConceptSchemeContainment)

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Wed, 07 Nov 2007 01:13:37 +0100
Message-ID: <47310331.2060906@mondeca.com>
To: "Miles, AJ (Alistair)" <A.J.Miles@rl.ac.uk>
Cc: public-esw-thes@w3.org

Hi all

I missed certainly the more recent discussions on that issue, but here 
are a few thoughts about it. Sorry if I revisit beaten tracks.

1. I definitely would like to have skos:inScheme and rdfs:isDefinedBy 
kept separate. If I read the RDF specification correctly at 
http://www.w3.org/TR/rdf-schema/#ch_isdefinedby, rdfs:isDefinedBy "is 
used to indicate a resource defining the subject resource".
Does a skos:ConceptScheme define the concepts it contains (whatever that 
containment means)? Don't think so. More below in point 2.
And : Concepts can be defined by one or several resources without any 
concept scheme being explicitly stated.
For example this looks correct to me :
<http://www.eionet.europa.eu/gemet/concept/7> rdfs:isDefinedBy  
<http://www.eionet.europa.eu/gemet/gemet-skoscore.rdf>
<http://www.eionet.europa.eu/gemet/concept/7> rdfs:isDefinedBy 
<http://www.eionet.europa.eu/gemet/gemet-translations>
<http://www.eionet.europa.eu/gemet/concept/7> rdfs:isDefinedBy 
<http://www.eionet.europa.eu/gemet/gemet-backbone.rdf>

Although neither of the object resources provide a complete definition 
of the concept, each of them provides a part of it, as elements of RDF 
descriptions. And they are clearly documents (information resources).
But, supposing (which is not the case) we declare 
<http://www.eionet.europa.eu/gemet/> to be concept scheme, it seems a 
complete different story to have
<http://www.eionet.europa.eu/gemet/concept/7> skos:inScheme 
<http://www.eionet.europa.eu/gemet/>

2. How can one find out all the concepts in a concept scheme in an open 
world, if there is no explicit declaration of some inverse property of 
skos:inScheme? Do I have to query the whole Web to know which concepts 
declare to be in the scheme at hand? Should not the owner of the concept 
scheme URI be able to provide ways to find out all concepts in the 
current scheme? At some point we had this skos:hasTopConcept, and I 
understood implicitely that from those top concepts, you just query down 
the tree following the "narrower" links, and whatever you find is in the 
scheme too. But what does that mean in an open world? What is the graph 
I'm supposed to query to find out? And what if the broader-narrower 
relation can cross concept schemes, as had been proposed?
Just thinking aloud (it's getting late) : would it be a silly idea to 
recommend that a skos:ConceptScheme would be defined by an RDF file 
giving the full, authoritative list of all concepts declared by the 
concept scheme owner/publisher to be currently in that scheme, such as.
ex:MyConceptScheme     rdfs:isDefinedBy     
ex:MyConceptSchemeConceptsListing.rdf

A a side remark about Guus pointing the lack of such declarations in 
OWL, I don't think this points to a particularity of SKOS vs OWL, but 
rather to an under-specification of OWL concerning the distinction 
between an ontology as an abstract scheme and the RDF document(s) which 
define(s) its elements. The containment issue is no more solved in OWL 
than it is in SKOS, and it is not different. The "open world assumption" 
of OWL is just waving off the issue.
People so far have mostly taken for granted that an OWL ontology is 
(contained in) the ontology document 'describing it' (plus the possible 
imported ones). But although OWL clearly specifies than an ontology is 
an RDF graph, it's nowhere explicit in the specification (Guus will 
correct me if I am wrong) that this graph should be contained in a 
single RDF document (there again, plus the imported stuff). It is 
recommended to identify the ontology by the xml:base URI, but several 
OWL/RDF documents can use the same xml:base and hence each 
define/describe parts of the same ontology (as the different RDF files 
of GEMET describe the same concept scheme) , without any way for one of 
those documents to say : warning, here is only one part of the ontology, 
other parts can be found there and there (supposing the publisher knows 
about them).

So maybe the difference between SKOS and OWL on that issue is the 
attention this group has brought to it, whereas that one had overviewed 
it. And actually, in my daily practice of OWL I miss such expressivity 
for ontology containment. We have a practical workaround in Mondeca 
applications where any ontology we use is always contained in what we 
call a "workspace". But those are "closed world" solutions. But maybe 
SKOS use cases and users have more closed world applications in mind 
than OWL had, that's why we saw this containment issue better.

Bernard

Miles, AJ (Alistair) a écrit :
> -----Original Message-----
> From: Miles, AJ (Alistair) 
> Sent: 06 November 2007 14:58
> To: SWD WG
> Subject: RE: [SKOS] inScheme and rdfs:isDefinedBy (cf. ISSUE-36 ConceptSchemeContainment)
>
> Hi all,
>
> I agree with Antoine to re-open ISSUE-36. 
>
> I also agree that there may be important differences between the semantics of rdfs:isDefinedBy and skos:inScheme, such that one cannot be a sub-property of the other. 
>
> I suggest we divide the problem into two: 
>
> First, we decide what we want to express. 
>
> Then, we look at existing vocabulary, in particular rdfs:isDefinedBy and skos:inScheme, and see if we can use it. If not, we invent new vocabulary.
>
> When discussing the first point, we must bear in mind that, as Guus has pointed out, OWL has no vocabulary for explicitly stating a relationship between a class, property or individual and the ontology in which it is defined. Yet, OWL applications have worked fine so far without need for any such vocabulary. Therefore, we must carefully consider which use cases establish a firm requirement for such vocabulary in SKOS, and why there are no analogous use cases for OWL. I.e. why is SKOS special?
>
> To stimulate discussion of the first point only, I've written some ideas down at:
>
> [1] <http://www.w3.org/2006/07/SWD/wiki/SkosDesign/ConceptSchemes/DiscussionPiece>
>
> Note that this is not a proposal, just a discussion piece, illustrating one possible point of view and some of its consequences.
>
> Cheers,
>
> Alistair.
>
>  
>
> --
> Alistair Miles
> Research Associate
> Science and Technology Facilities Council Rutherford Appleton Laboratory Harwell Science and Innovation Campus Didcot Oxfordshire OX11 0QX United Kingdom
> Web: http://purl.org/net/aliman
> Email: a.j.miles@rl.ac.uk
> Tel: +44 (0)1235 445440  
>
>   
>> -----Original Message-----
>> From: public-swd-wg-request@w3.org
>> [mailto:public-swd-wg-request@w3.org] On Behalf Of Antoine Isaac
>> Sent: 30 October 2007 17:00
>> To: SWD WG
>> Subject: [SKOS] inScheme and rdfs:isDefinedBy (cf. ISSUE-36
>> ConceptSchemeContainment)
>>
>>
>> Hello,
>>
>> Following the discussion today I have the following action:
>>
>>     
>>> *[NEW]* *ACTION:* Antoine to summarise inScheme vs isDefinedBy and 
>>> decide whether or not to reopen the issue. [recorded in 
>>> http://www.w3.org/2007/10/30-swd-minutes.html#action03]
>>>       
>> Minutes of the Oct 9 Face-to-face meeting [1] present the following 
>> (parts of a) resolution:
>>
>>     
>>>> 1. for historical reasons, inscheme is kept as a subprop of 
>>>> isDefinedBy we agree 3. that deprecating skos:inScheme (using 
>>>> approporiate owl
>>>> vocab) is part of the accepted proposal
>>>>         
>> These extend Alistair's proposal for concept scheme semantics [3], 
>> which is also part of the resolution:
>>
>>     
>>> The SKOS Primer also defines best practices for using
>>>       
>> rdfs:isDefinedBy
>>     
>>> to explicitly state the relationship between a SKOS conceptual 
>>> resource and the concept scheme in which it is defined.
>>>       
>> HOWEVER, it is questionable whether inScheme has an original meaning 
>> compatible with rdfs:isDefinedBy
>>
>> As RDFS spec puts it [4]
>>
>>     
>>> |rdfs:isDefinedBy| is an instance of |rdf:Property|
>>> <http://www.w3.org/TR/rdf-schema/#ch_property> that is used to 
>>> indicate a resource defining the subject resource. This
>>>       
>> property may
>>     
>>> be used to indicate an RDF vocabulary in which a resource
>>>       
>> is described.
>>
>> As SKOS core guide puts it [5]:
>>
>>     
>>> where you would like to assert that a concept is a part of a 
>>> particular concept scheme, use the |skos:inScheme 
>>> <http://www.w3.org/2004/02/skos/core/spec/#inScheme>| property,
>>>       
>> The two properties therefore seem to have different motivations: 
>> rdfs:isDefinedBy is linked to the notion of definition, skos:inScheme 
>> to the one of containment. Elisa has cited the following in our last 
>> telecon:
>>
>>     
>>>  If it's at all helpful, the "formal" definition of a
>>>       
>> "concept system" 
>>     
>>> from ISO 1087 is "a set of concepts structured according to the 
>>> relations among them".
>>>       
>> Furthermore, as SKOS spec [6] puts it:
>>
>>     
>>> A concept may be a member of more than one concept scheme.
>>>       
>> This could raise a problem: rdfs:isDefinedBy is not functional so can 
>> point at several resources. But it is expected that all these 
>> resources are expected to give a description of the defined resource. 
>> I don't think this would be the case for all the concept scheme a 
>> concept is member of. A concept will be for sure defined in some 
>> concept scheme, but I don't expect it to be defined in all the concept 
>> schemes it belongs to.
>>
>> As a consequence, I PROPOSE TO RE-OPEN THIS ISSUE (which by the way is 
>> not closed, cf [7]) and make the following proposal for a resolution:
>>
>> RESOLUTION: skos:inScheme is not deprecated, skos:inScheme is not a 
>> subproperty of rdfs:isDefinedBy. In accordance [3] can be kept, but 
>> adding inScheme in the proposed vocabulary as well as domain and range 
>> statements for this property. It should also include the following
>> sentence: "The SKOS Primer also defines best practices for using 
>> skos:inScheme to explicitly state the relationship between a SKOS 
>> conceptual resource and the concept scheme(s) to which it belongs."
>>
>>
>> Antoine
>>
>>
>> [1] http://www.w3.org/2007/10/09-swd-minutes.html
>> [2]
>> http://lists.w3.org/Archives/Public/public-swd-wg/2007Oct/0109.html
>> [3]
>> http://www.w3.org/2006/07/SWD/wiki/SkosDesign/ConceptSchemes/M
>> inimalProposal?action=recall&rev=1
>> [4] http://www.w3.org/TR/rdf-schema/#ch_isdefinedby
>> [5] http://www.w3.org/TR/swbp-skos-core-guide/#secscheme
>> [6] http://www.w3.org/TR/swbp-skos-core-spec/#inScheme
>> [7] http://www.w3.org/2006/07/SWD/track/products/3
>>
>>
>>
>>     
>
>  
>
>
> --
> Alistair Miles
> Research Associate
> Science and Technology Facilities Council
> Rutherford Appleton Laboratory
> Harwell Science and Innovation Campus
> Didcot
> Oxfordshire OX11 0QX
> United Kingdom
> Web: http://purl.org/net/aliman
> Email: a.j.miles@rl.ac.uk
> Tel: +44 (0)1235 445440 
>
>
>
>   

-- 

*Bernard Vatant
*Knowledge Engineering
----------------------------------------------------
*Mondeca**
*3, cité Nollez 75018 Paris France
Web:    www.mondeca.com <http://www.mondeca.com>
----------------------------------------------------
Tel:       +33 (0) 871 488 459
Mail:     bernard.vatant@mondeca.com <mailto:bernard.vatant@mondeca.com>
Blog:    Leçons de Choses <http://mondeca.wordpress.com/>
Received on Wednesday, 7 November 2007 00:13:55 UTC

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