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Re: faceted classification

From: NJ Rogers, Learning and Research Technology <Nikki.Rogers@bristol.ac.uk>
Date: Tue, 23 Mar 2004 12:26:12 -0000
To: Leonard Will <L.Will@willpowerinfo.co.uk>, "Miles, AJ (Alistair)" <A.J.Miles@rl.ac.uk>
Cc: "Douglas Tudhope (E-mail)" <dstudhope@glam.ac.uk>, "Stella Dextre Clarke (E-mail)" <SDClarke@lukehouse.demon.co.uk>, "'public-esw-thes@w3.org'" <public-esw-thes@w3.org>
Message-ID: <9010000.1080044772@localhost.localdomain>

Hi All

I find Leonard's reply helpful here.

Looking at

>Detergents
>      <detergents by form>
>      liquid detergents
>      gel detergents
>      powder detergents
>
>      <detergents by scent>
>      citrus scented detergents
>         lemon scented detergents
>         orange scented detergents
>      pine scented detergents
>
>      <detergents by brand name>
>      Persil detergents
>      Daz detergents
>      Surf detergents

from an rdf-world point of view, I can imagine some rdf:resource, X, and I 
might want to say:

[X] type [detergent]
[X] physical state [powder]
[X] scent [citrus scents]
....

This is not N3 or anything, but you can see what I'm saying,
(X has an rdf:type of detergent, its physical state is powder etc). And 
here 'detergent', 'powder' etc would be encoded as skos concepts for this 
particular thesaurus.

But what to do about our 'facets': physical state, scent etc? We don't want 
them to be treated like skos:concepts because basically they are 
rdf:properties.  Therefore they form an extensional part of skos:core, I'm 
thinking. i.e. to migrate a thesaurus that includes facets in the sense of 
fundemental categories, one should give these facets as properties:

rdf:Property rdf:ID="physicalState"
	<rdfs:label>Physical State<rdfs:label>
	<rdfs:subPropertyOf rdf:resource="skos#facet"/>
	<rdfs:range rdf:resource="#Solids>
	<rdfs:range rdf:resource="#Gels>
	....
	<rdfs:comment>
	</rdfs:comment>
</rdf:Property>


where any facet is declared as a subproperty of skosfacet, say, & which is 
not to be linked into OWL or rdfs.

Putting in the range resources (which should all be skos:Concept's) would 
enable an application to switch views on instance data in the way Leonard 
describes below. And the hierarchy of skos concepts would enable an 
application to determine that concepts under 'Solids' also are in the range 
of the physicalState property, and so on.

As for the 'backwards pointer' - the ability to express for any given skos 
Concept its facet - I haven't thought through whether or not that is 
necessary.

Nikki







--On Monday, March 22, 2004 14:59:17 +0000 Leonard Will 
<L.Will@willpowerinfo.co.uk> wrote:

>
> In message
> <350DC7048372D31197F200902773DF4C04944189@exchange11.rl.ac.uk> on Mon,
> 22 Mar 2004, "Miles, AJ (Alistair)" <A.J.Miles@rl.ac.uk> wrote
>> Hi Doug, Leonard, Stella,
>>
>> I just read the article [1] that Doug forwarded.  I was wondering if you
>> could help to me to clear something up.
>>
>> I have so far come across two meanings for 'faceted classification':
>>
>> (Sense 1)
>>
>> A set of things are 'classified' according to their properties.  For
>> example (from [1]) a set of detergents are classified by 'brand name',
>> 'form', 'scent', 'agent', 'effect on agent' and 'special property'.  In
>> this sense, each of these properties represents a 'facet' through which
>> the set of instances can be viewed.
>>
>> (Sense 2)
>>
>> A set of 'concepts' are grouped according to their most primitive type.
>> For example, the concept 'marble' is placed in the 'materials' facet.
>> The concept 'insects' is placed in the 'organisms' facet.  In this
>> sense, a 'facet' is essentially a primitive class, and every member of a
>> facet group is either an instance or a sub-class of that class.
>>
>> So my first question is: have I described these two senses accurately
>> (or am I missing something)?
>
> Alistair
>
> Congratulations on recognising at first reading an ambiguity that I've
> been banging on about for years!
>
> The terminology of faceted classification is indeed not well controlled.
> :-(
>
> Some people use the expression "subfacets" for your sense 1 and
> "fundamental facets" for your sense 2, but I think that this is
> confusing because they are indeed different, and not specific types of
> some more general things called "facets".
>
> The main need, as you point out, is to distinguish these two senses and
> to use different names for them. The choice as to which should be given
> the word "facets" is difficult, as there is warrant for either, but the
> interpretation I have advocated, and which is in the draft British
> Standard currently under preparation, is to use "facets" for your sense
> 2, i.e. "fundamental facets", sometimes called "fundamental categories".
>
> For sense 1, an accepted terminology is to say that concepts are grouped
> into "arrays" according to specified "characteristics of division". The
> "characteristic of division" is shown in a node label, after the word
> "by". These node labels are not descriptors, but explain the grouping of
> concepts in the array that they introduce. You then have a hierarchy
> such as the following which shows three arrays:
>
> detergents
>      <detergents by form>
>      liquid detergents
>      gel detergents
>      powder detergents
>
>      <detergents by scent>
>      citrus scented detergents
>         lemon scented detergents
>         orange scented detergents
>      pine scented detergents
>
>      <detergents by brand name>
>      Persil detergents
>      Daz detergents
>      Surf detergents
>
> Note that in this case the arrays all list kinds of detergents. If you
> wanted to separate out the properties from the detergents, you would
> have distinct hierarchies such as
>
> scents
>      citrus scents
>         lemon scents
>         orange scents
>
> physical states
>      solids
>         powders
>      gels
>      liquids
>
> and these would belong to different [fundamental] facets.
>
> The AAT puts "scents" (i.e. "odors") into an  "environmental concepts"
> facet and "powders" into a "materials" facet under the node label
> <materials by physical form>.
>
> In this case these terms would come together with detergents only when
> both descriptors were assigned to an item when that item was being
> indexed.
>
> I hope other people agree with this description.
>
> Leonard
>
>
>
>
>
>
>
>
>
>>
>> My second question is: are there any other senses of 'faceted
>> classification' worth considering?
>>
>> Finally: if my analysis is correct, these two senses describe quite
>> different systems of organisation (*).  So would it be useful in the
>> short term to come up with unambiguous names for these two meanings?
>> For example, we could refer to sense 1 as 'classification by
>> description' and sense 2 as 'primitive classification'.
>>
>> Please let me know what you think.
>>
>> Yours,
>>
>> Alistair.
>>
>>
>> (*) although sense 2 could be viewed as a special case of sense 1, in
>> which concepts are classified according to the value of a 'primitive
>> type' property - i.e. 'primitive type' represents a 'facet' in sense 1!
>>
>> [1] <http://www.miskatonic.org/library/facet-web-howto.html>
>>
>> ---
>> Alistair Miles
>> Research Associate
>> CCLRC - Rutherford Appleton Laboratory
>> Building R1 Room 1.60
>> Fermi Avenue
>> Chilton
>> Didcot
>> Oxfordshire OX11 0QX
>> United Kingdom
>> Email:        a.j.miles@rl.ac.uk
>> Tel: +44 (0)1235 445440
>>
>>
>
> --
> 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/> -----------------
>
>



----------------------
NJ Rogers, Technical Researcher
(Semantic Web Applications Developer)
Institute for Learning and Research Technology (ILRT)
Email:nikki.rogers@bristol.ac.uk
Tel: +44(0)117 9287096 (Direct)
Tel: +44(0)117 9287193 (Office)
Received on Tuesday, 23 March 2004 07:17:15 GMT

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