W3C home > Mailing lists > Public > public-swd-wg@w3.org > February 2008

[SKOS] on ISSUE-71 and ISSUE-74

From: Alistair Miles <alistair.miles@zoo.ox.ac.uk>
Date: Thu, 21 Feb 2008 18:50:01 +0000
Message-ID: <47BDC7D9.3080503@zoo.ox.ac.uk>
To: public-swd-wg@w3.org, public-esw-thes@w3.org

Dear all,

I've been trying to collect my thoughts on issues 71 and 74. Here's 
where I've got to so far.

=== Background ===

Antoine's email of the 17 Feb [1] discusses both issue 71 and issue 74, 
and proposes resolutions to both. This email contains an argument for a 
fundamental distinction between "paradigmatic" versus "mapping" 
relations based on notions of authority and semantic commitment, and 
hence for parallel vocabularies.

Antoine's first email of 19 Feb [2] makes a new proposal for resolution 
of issue 71, based on the argument of 17 Feb.

Antoine's second email of 19 Feb][3] makes a new proposal for resolution 
of issue 74, again based on the argument of 17 Feb.

[1] http://lists.w3.org/Archives/Public/public-swd-wg/2008Feb/0062.html
[2] http://lists.w3.org/Archives/Public/public-swd-wg/2008Feb/0076.html
[3] http://lists.w3.org/Archives/Public/public-swd-wg/2008Feb/0077.html

=== Preamble ===

First, a point of pedantry. "Paradigmatic" is used in BS 8723-2 to 
denote links that are inherent in the meaning of the linked concepts.

The idea in SKOS was always that broader, narrower and related, whether 
used within a concept scheme or between concept schemes, denote links 
between concepts which are inherent in the meaning of the linked 
concepts. Therefore, broader, narrower and related mapping links are 
just as "paradigmatic" as broader, narrower or related links within a 
concept scheme.

Below, I use "intra-scheme links" to mean broader, narrower or related 
links between concepts in the same scheme, and I use "inter-scheme 
links" to mean broader, narrower or related links between concepts in 
different schemes.

=== Discussion ===

If we are going to have separate, parallel vocabularies in SKOS for 
intra-scheme versus inter-scheme links, then I want to make sure we have 
clear, sound and valid reason(s) for doing so. Note especially that no 
analogous pattern is present in OWL, and therefore we need to justify 
our different approach.

Let me start by trying to restate Antoine's position on intra-scheme 
links, as points A-E below:

A. The activity of constructing a concept scheme is typically carried 
out by a single authority. This activity results in, among other things, 
a set of intra-scheme links between the concepts of the scheme. The 
properties skos:broader, skos:narrower and skos:related should be used 
by such an authority to represent these intra-scheme links.

B. Because the properties skos:broader, skos:narrower and skos:related 
are used, for the most part, by an authority as described above, then 
they can in general be relied upon to carry a certain degree of 
authority, without needing to question the provenance of any graph in 
which they are used.

C. The activity of constructing a concept scheme generally follows a 
well-defined methodology, and is carried out by a single authority in 
support of a known application. Therefore, the intra-scheme links 
between concepts can generally be relied upon to carry a certain degree 
of semantic soundness or intellectual consistency.

D. Because the properties skos:broader, skos:narrower and skos:related 
are used, for the most part, to represent intra-scheme links that result 
from such an activity, then they can in general be relied upon to carry 
a certain degree of semantic soundness or intellectual consistency, 
without needing to question the provenance of any graph in which they 
are used.

E. The properties skos:broader, skos:narrower and skos:related may be 
used in other ways, however because they are mostly used as described 
above, then they can be trusted to, in general, represent intra-scheme 
links with a relatively high degree of authority and intellectual 
soundness or consistency, without needing to question the provenance of 
any graph in which they are used.

Let me now try to restate Antoine's position on inter-scheme links, as 
points F-H below:

F. The activity of constructing a mapping between two concept schemes is 
typically carried out by a single authority, which differs from the 
authorities who were responsible for developing each individual scheme. 
Such an activity results in a set of inter-scheme links between the 
concepts of the two schemes. The properties skos:broadMatch, 
skos:narrowMatch, skos:relatedMatch and skos:exactMatch should be used 
to represent these inter-scheme links.

G. Because the properties skos:broadMatch, skos:narrowMatch, 
skos:relatedMatch and skos:exactMatch are used, for the most part, as 
described above, they cannot in general be relied upon to carry the 
authority of either party responsible for the construction of the 
individual concept schemes.

H. Although the activity of constructing a set of mapping links between 
schemes might follow a well-defined methodology, the process is 
fundamentally different from the process of constructing links between 
concepts within a scheme, because the mapping authority has no control 
over the scope or organisation of each of the mapped schemes, and 
therefore has to cope with a wide variety of content and structure. 
Therefore, links that result from such an activity are generally more 
variable, less intellectually consistent or sound, than are links which 
result from the construction of a concept scheme.

I. Because the properties skos:broadMatch, skos:narrowMatch, 
skos:relatedMatch are used, for the most part, to represent inter-scheme 
links which result from such an activity, they generally carry a lower 
degree of semantic soundness or intellectual consistency than do 
skos:broader, skos:narrower and skos:related.

J. The properties skos:broadMatch, skos:narrowMatch, skos:relatedMatch 
may be used in other ways, however because they are mostly used as 
described above, then they can be trusted to, in general, represent 
inter-scheme links with a relatively low degree of authority and 
intellectual soundness or consistency, without needing to question the 
provenance of any graph in which they are used.

=== My Position ===

Let us consider the ways in which links between concepts might differ.

There are links which are "authoritative", and there are links which are 
not. There are links which are well-engineered and intellectually sound, 
and there are links which are not. There are links which span concept 
schemes, and there are links which do not. These are three orthogonal 
dimensions. There is also, of course, a fourth dimension of basic 
paradigmatic meaning, i.e. whether the link is broader, narrower or 
related, which is again orthogonal to the first three.

Antoine's position, as stated above, is that skos:broader and 
skos:broadMatch share the same paradigmatic meaning, however 
skos:broader is typically (but not always) intra-scheme, more 
authoritative and more intellectually consistent, whereas 
skos:broadMatch is typically (but not always) inter-scheme, less 
authoritative and less intellectually consistent.

This is quite a load for each of these properties to carry. My concern 
is that, in practice, neither of these properties (skos:broader, 
skos:broadMatch) can be relied upon to carry anything other than their 
basic, paradigmatic meaning, and that therefore, in practice, they are 
at best redundant, and at worst misleading. To use an analogy, if SKOS 
were a security-critical technology, then any application which relied 
on a fundamental difference between skos:broader and skos:broadMatch 
would have a serious vulnerability.

Authority depends on provenance, as does trust in intellectual 
soundness. As a general design principle, I say that no property should 
ever be expected to carry greater authority or trust than another 
property, because such an expectation cannot be supported in practice. 
Authority and trust can only be conveyed, via provenance, outside the graph.

Kind regards,

Alistair.

-- 
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 Friday, 22 February 2008 05:44:35 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:07:52 UTC