ISSUE 186 - draft response

Note: this is a *draft reponse*

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.  

@@insert text here from Alistair's email
http://lists.w3.org/Archives/Public/public-esw-thes/2008Oct/0041.html

> 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 [3] 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 (for example, see discussion
    about 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 
[4].


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://www.w3.org/TR/2008/WD-skos-reference-20080829/#rationale
[4] http://www.w3.org/TR/skos-primer/#secskosspecialization