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Re: ISSUE-186 [Re: SKOS comment: Last Call Working Draft]

From: Alistair Miles <alistair.miles@zoo.ox.ac.uk>
Date: Tue, 2 Dec 2008 13:48:28 +0000
To: public-swd-wg@w3.org
Message-ID: <20081202134828.GE24871@skiathos>

This doesn't appear in tracker, trying again with slightly different
subject line.

On Mon, Dec 01, 2008 at 11:49:09PM +0100, Guus Schreiber wrote:
> Dear Michael,
> Dear Michael,
> Thanks again for your comment below (from [1]), which we have
> filed as ISSUE 186 [2].
> [..]
> > We also see potential problems in deriving the mapping
> > relations skos:broadMatch and skos:narrowMatch from
> > skos:broader and skos:narrower. In ISO standard and current
> > practices many multilingual thesauri did not use broader or
> > narrower to indicate the mapping relations. SKOS should
> > revisit those standards and follow the current standards'
> > development to make sure SKOS is consistent in representing
> > the indicators used by standards (and the thesauri following
> > those standards) for so many years.
> Quating from Alistair Miles' response [3]:
> "The SKOS mapping properties have their roots in ISO 5964 and have been 
> informed more recently by BS 8723 part 4. I don't have ISO 5964 to hand 
> so I may not quote precisely from it here, hopefully others can correct 
> me if I make any glaring errors. ISO 5964 introduced the notions of 
> exact, inexact and partial
> correspondance between thesaurus descriptors. These provided
> inspiration for the SWAD-Europe report on inter-thesaurus mapping, which 
> first described the use of the SKOS Mapping RDF schema [4].
> Note in particular that the "partial" correspondance as described in ISO 
> 5964 indicated that the meaning of one descriptor *either* subsumes *or* 
> is subsumed by the meaning of the other. Hence [4] refined the notion of 
> a partial mapping to provide broad and narrow mapping properties, which 
> are clearly more useful than the ambiguous "partial". We felt this was  
> consistent with the intention of ISO 5964 (see also note [5]).
> BS 8723 part 4 ("interoperability between vocabularies") provides a clear 
> (IMO) discussion of mapping between extant vocabularies. It illustrates 
> the use of standard hierarchical and associative relationships (BT, NT 
> and RT), in addition to an equivalence (EQ) relationship, to assert 
> mappings between vocabularies, in what they call "differentiated 
> mappings". These directly correspond to the skos:broadMatch, 
> skos:narrowMatch, skos:relatedMatch and skos:exactMatch properties. (See 
> also note [6].)
> We realise that "undifferentiated mappings" (where the nature of the 
> correspondance is not specified) may represent the majority of real world 
> mapping data. However, "differentiated mappings" are also an important 
> resource, and are being constructed at scale e.g. by FAO.
> Hence the current design for SKOS is based on a perceived consensus for 
> mapping between vocabularies, which is to ground the different types of 
> mapping relationship in the notions of hierarchical and associative 
> relationships, and we believe that this consensus is consistent with 
> existing standards."
> > In addition, when mapping systems that are structurally
> > heterogeneous (e.g., classification systems and thesauri), the
> > links established through mappings have no hierarchical
> > implications at all.
> >
> > Currently, skos:broader is used both for the hierarchical
> > relationship between classes as well as between concepts.
> > Mapping relations that are subproperties of
> > skos:broader/skos:narrower are not able to sufficiently
> > support interoperability between structurally heterogeneous
> > systems.
> We understand your point. SKOS mapping relations cannot solve
> the heterogeneity of vocabularies and it is not possible to
> prevent wrong usage of the mapping relations. However, we think
> that the mapping relations do provide an important mechanism.
> Also, people can use, next to the broader/narrower, other
> mapping relations such as closeMatch and relatedMatch, which
> might be more suitable in heterogeneous cases.
> We propose to add a note to the current text to clarify this point.
> > In addition, many different indicators of degree of mapping
> > have been used in integrated vocabularies, e.g., major
> > mapping, minor mapping, alternative mapping, and overlapping.
> > These may make the mapping properties even more complicated.
> > The solution here might again be to extend mapping properties.
> Our SKOS design rationale [5] is:
> [[
>    "The notion of a Knowledge Organisation System encompasses a
>     wide range of artefacts. There is thus a danger of
>     overcommitment in the SKOS schema, which could preclude the
>     use of SKOS for a particular application. In order to
>     alleviate this, in situations where there is doubt about the
>     inclusion of a formal constraint (e.g., seediscussion
>     on skos:hasTopConcept), the constraint has not been stated
>     formally. In such cases, usage conventions may be suggested,
>     or specialisations of the SKOS vocabulary may be used in
>     order to enforce constraints (see the SKOS Primer)."
> ]]
> So, we agree that extending the mapping properties might very
> well be a good idea, but we prefer to leave this to developers.
> See also the section in the SKOS primer on extension mechanisms
> [6].
> We hope you live with this response.
> Regards,
> Guus Schreiber
> [1]
> http://lists.w3.org/Archives/Public/public-swd-wg/2008Oct/0061.html
> [2] http://www.w3.org/2006/07/SWD/track/issues/186
> [3]  
> http://lists.w3.org/Archives/Public/public-esw-thes/2008Oct/0041.html
> [4] http://www.w3.org/2001/sw/Europe/reports/thes/8.4/
> [5] http://www.w3.org/TR/2008/WD-skos-reference-20080829/#rationale
> [6] http://www.w3.org/TR/skos-primer/#secskosspecialization
> [7] IMO ISO 5964 requires careful interpretation. From previous
> readings, I understood that ISO 5964 is primarily aimed at describing the 
> *process* of constructing a single multilingual thesaurus, *not* on 
> mapping between extant monolingual thesauri in either the same or 
> different languages. The notions of "exact", "inexact" and "partial" are 
> used to describe the types of correspondance that can be encountered 
> between different language components *during the process of constructing 
> a multilingual thesaurus*, with the implication being that anything other 
> than an exact correspondance must usually be mored closely aligned before 
> the thesaurus is finally published.
> [8] Although the main body of BS 8723-4 discusses mapping between 
> vocabularies (sections 5-8), where the assumption is that modifications 
> to each vocabulary cannot be made to improve the alignment, BS8723-5 also 
> discusses the process of constructing a single multilingual thesaurus 
> (section 9), where changes can be made to each language component to 
> improve the overall alignment of the thesaurus. IMO section 9, whilst  
> valuable, is out of place in BS8723-4, because the process of  
> constructing a single multilingual thesaurus (where language components 
> can be modified to improve alignment) is different from the process of 
> mapping between extant thesauri (where mappings have to describe aligment 
> as-is), and would be better treated in a separate document.

> begin:vcard
> fn:Guus Schreiber
> n:Schreiber;Guus
> org:VU University Amsterdam, Computer Science
> email;internet:schreiber@cs.vu.nl
> title:Prof. dr. 
> x-mozilla-html:FALSE
> url:http://www.cs.vu.nl/~guus/
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> end:vcard

Alistair Miles
Senior Computing Officer
Image Bioinformatics Research Group
Department of Zoology
The Tinbergen Building
University of Oxford
South Parks Road
United Kingdom
Web: http://purl.org/net/aliman
Email: alistair.miles@zoo.ox.ac.uk
Tel: +44 (0)1865 281993
Received on Tuesday, 2 December 2008 13:49:17 UTC

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