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FW: Modelling 'term-to-term' relationships in SKOS

From: Stella Dextre Clarke <sdclarke@lukehouse.demon.co.uk>
Date: Thu, 4 Mar 2004 09:36:12 -0000
To: <public-esw-thes@w3.org>
Message-ID: <000201c401cc$21d6fbf0$0402a8c0@DELL>

I agree with Leonard's comments below. Picking up on another point in
Alistair's earlier message, "US/UK Alts:

If distinguishing between US/UK alts is important, they could both be
represented as labels with language tags, treating US-English and
UK-English as separate languages.  E.g.

	<skos:prefLabel xml:lang="en-US">Color</skos:prefLabel>
	<skos:prefLabel xml:lang="en-GB">Colour</skos:prefLabel>

I suspect most of the time it will be sufficient to include US spelling
alts among the altLabels (if it is an english thesaurus), without
needing to add language tags.  This would be enough to ensure concepts
are picked up by searching yanks."

Direct immediate searching may not be the only need. If you want to use
the data to print out or present an on-screen display of the thesaurus
for human look-up, then you might want to present a British-spelt
version for UK users, an American spelt version for US users. You might
even want to give users an option to choose their dialect, just as they
might choose to display in French or German. For this purpose
undifferentiated altLabels are insufficient.

Stella Dextre Clarke
Information Consultant
Luke House, West Hendred, Wantage, Oxon, OX12 8RR, UK
Tel: 01235-833-298
Fax: 01235-863-298

-----Original Message-----
From: public-esw-thes-request@w3.org
[mailto:public-esw-thes-request@w3.org] On Behalf Of Leonard Will
Sent: 03 March 2004 18:21
To: public-esw-thes@w3.org
Subject: Re: Modelling 'term-to-term' relationships in SKOS

In message
<350DC7048372D31197F200902773DF4C047485F4@exchange11.rl.ac.uk> on Wed, 3

Mar 2004, "Miles, AJ (Alistair)" <A.J.Miles@rl.ac.uk> wrote
>I designed SKOS to be strictly concept-oriented.  In this view there 
>are only 'concepts' and 'labels'.
>In the concept-oriented view, 'antonymy' would be represented as a
>relationship between two concepts.  So in an imaginary thesaurus, 
>concept A (label 'Black') is opposite of concept B (label 'White').  As

>an extension of SKOS, the relationship 'is opposite of' would be 
>modelled as a sub-property of skos:SemanticRelation.

There are some cases where apparent antonyms are alternative labels for 
the same concept. "Dryness" and "wetness" for example are both possible 
labels for the concept of "moisture content". (The "half-full" or 
"half-empty" situation.)

>Equivalence between terms:
>In the concept-oriented view, a label is simply a string.  Therefore, 
>there is no notion of 'equivalence' between labels.
>A label may be used as a label for more than one concept.

This worries me. A label is only of use if it identifies the thing it 
labels. I may have three jars labelled "coffee", of which one contains 
coffee, one contains tea and the other contains sugar, but this is not 
the sort of situation we should accept.

Did you mean to say that a concept may have more than one label? That is

certainly true, and two labels that refer to the same concept could 
reasonably be said to be "equivalent".

>However, a label is always considered to be empty of meaning.
>Therefore, there is no notion of 'equivalence' between a label and a 

Perhaps not "equivalence" but still a close association. The label is a 
convenient way of referring to the concept, avoiding the need to write 
out the scope note in full every time you want to refer to it. If I 
label a jar "coffee", "café" or "641.3373", those symbols are by no 
means empty of meaning; they indicate the same substance even though the

character strings are not "equivalent" to the substance.

>SKOS supports a notion of 'equivalence' between concepts.  This may
>either be modelled as a sub-property of skos:SemanticRelation (i.e. an 
>intra-thesaurus relation) or a sub-property of skos-map:SemanticMapping

>(i.e. an inter-thesaurus relation).
>E.g. SKOS-Mapping contains the property skos-map:exactMapping, which
>could be used to express an 'exact equivalence' relationship between 
>two concepts.

>E.g. SKOS-Mapping contains two properties skos-map:MajorMapping and
>skos-map:MinorMapping, which could be used to express greater or lesser

>degrees of 'equivalence' between concepts.

As you have indicated, equivalence between concepts is something that 
should arise only when mapping between different thesauri.

If two concepts within a single thesaurus are exactly equivalent, I see 
no need for them both to be present. They should be combined, as there 
is only one concept, not two.

If there is partial equivalence between concepts in a single thesaurus, 
then either one is a narrower term of the other or else there is an area

of overlap (e.g. "ships" and "boats"). In the latter case the scope of 
each concept should if possible be redefined so as to eliminate this 
overlap, as it will lead to uncertainty in using the thesaurus. An 
associative link may then be made between the two related concepts.

It must be difficult to differentiate between MajorMapping and 
MinorMapping, but it is probably helpful to have these to indicate large

or small extents of overlap.
>Final word:
>This is how I think of it.  To switch from a 'term-oriented' view to a 
>'concept-oriented' view, instead of 'term' think 'concept+label'.

Or 'concept + as many labels as necessary' (of which one may be 
designated as the "preferred" label or "descriptor").

>What does everyone think?

My tuppence worth.

Willpower Information       (Partners: Dr Leonard D Will, Sheena E Will)
Information Management Consultants              Tel: +44 (0)20 8372 0092
27 Calshot Way, Enfield, Middlesex EN2 7BQ, UK. Fax: +44 (0)870 051 7276
L.Will@Willpowerinfo.co.uk               Sheena.Will@Willpowerinfo.co.uk
---------------- <URL:http://www.willpowerinfo.co.uk/> -----------------
Received on Thursday, 4 March 2004 04:59:07 UTC

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