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Re: Exactly what does broader/narrower mean?

From: Leonard Will <L.Will@willpowerinfo.co.uk>
Date: Mon, 19 Feb 2007 18:15:59 +0000
Message-ID: <+5rt7WOfle2FFArg@mail.willpowerinfo.co.uk>
To: public-esw-thes@w3.org

In message <000c01c75425$f53f2db0$0300000a@DELL> on Mon, 19 Feb 2007,
Stella Dextre Clarke <sdclarke@lukehouse.demon.co.uk> wrote
>If the vocabulary is a taxonomy or a classification scheme, then the rules of
>hierarchy tend to be much looser. It is convenient in a library or a
>bookshop to be able to browse through, for example, the Chemistry
>shelves to find books about chemical elements, chemical laboratories and
>even chemists. (Read more about this in the forthcoming BS 8723-3.)
>So to use your example, a thesaurus should not allow German politicians
>to be treated as a narrower term of Germany (although conceivably these
>could be considered as related terms). But a taxonomy or a classification
>scheme could allow you to organise these classes hierarchically if you

I have a slightly different approach to this, which probably depends on
a different interpretation of the word "hierarchy".

I agree with Stella that the broader/narrower relationship should be
restricted in the ways she says are specified in BS8723-2.

A "hierarchy" as shown in a classification scheme may or may not be an
example of broader/narrower relationships, depending on whether the two
linked terms belong to the same facet or not. Thus

    prime ministers



are valid BT/NT relationships, because in both cases the terms come from
the same facet, "people" or "places" respectively.

The relationship


is not a BT/NT relationship, because the terms come from different
facets. In this case we are expressing a compound concept, "Germany :

It is clear that the relationship is not hierarchical, because it would
be perfectly valid to express it as


if you prefer the citation order of facets "people - place" rather than
"place - people".

The point is that a classification scheme provides for combination or
"pre-coordination" of concepts in this way. A thesaurus generally deals
with the elementary concepts, for use in post-coordinate systems where
concepts are combined at the time of searching.

There is a subtle complication in the case cited of "German
politicians", which is not the same concept as "politicians in Germany".
In a classification scheme this could be expressed as arrays within the
"people" facet, with two criteria of division, where the hierarchical
relationships are indeed valid BT/NT:

    (people by occupation)
        (politicians by nationality)
        French politicians
        German politicians


    (people by nationality)
    French people
    German people
        (German people by occupation)
        German politicians

The node labels that I have shown in parentheses are often omitted, but
including them makes the structure clearer.

In the example of chemical elements, a classification may well specify
these under a discipline such as "chemistry". Again we have compound
concepts, combining terms from a "discipline" facet with terms from a
"materials" facet. Chemical elements may well occur combined with other
disciplines, such as "jewellery - gold" or "fuel technology - hydrogen".
In none of these cases does the combination imply a BT/NT relationship
between the component concepts.

I don't think that SKOS has yet been developed to deal fully with
compound concepts, but I do think it is important that these compounds
should be distinguished from BT/NT relationships.

Leonard Will

Willpower Information       (Partners: Dr Leonard D Will, Sheena E Will)
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Received on Monday, 19 February 2007 22:28:51 UTC

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