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RE: Definition of "facet"

From: Aida Slavic <aida@acorweb.net>
Date: Mon, 1 Mar 2004 14:04:09 -0000
To: <public-esw-thes@w3.org>
Message-ID: <AAEKLFPLCPPCFCOACDKIGEKMCJAA.aida@acorweb.net>

Leonard,

My concern with any definition we would accept is related to the
functionality
this may imply

I have in mind the following:

1) facets in expressing semantic (logical hierarchy and poly-hierarchy)
here is where the issue of facet/array and inheritance comes

	- a little digression may be relevant here:
	Svenonius suggested that for m2m handling of vocabulary there should be
provision
	for indicating the difference between hierarchy types:
	logical hierarchy (one concept-one hierarchy) and perspective hierarchy
	(one concept more than one hierarchy)
	first hierarchy type is good for broadening and narrowing search in IR when
vocabulary
	covers single subject area (e.g. thesauri)
	second hierarchy type is paramount for disambiguation (when vocabulary
covers
	universal knowledge area e.g. classifications)

the question is: if we accept to declare that something is a facet in
SKOS/OWL does this mean that
only logical hierarchies are allowed... and that the same concept will not
occur
in other hierarchies within the same KOS irrespective whether the concepts
are naturally
context free and irrespective the coverage of KOS
(thinking here of polysems (culture, organization, democracy) and other
vague concepts such as water, marble, cell etc. and the way they may be
treated in
special and general KOS)

2) facets in expressing syntax/structure
(i.e. combining terms from different facets)
here is where the issue of encoding of an open set of facets
is important. Different KOS need to declare their own facets/arrays
on a top of which one could later build applications for handling syntax
roles and rules

I think the care should be taken (if it hasn't been already)
to allow for both.

There is no agreement on the semantic of fundamental facets so pinning
down the semantic can hardly be the ONLY reason for stating the facet.
Thesauri usually declare facets for vocabulary building/control/management
while classification systems, apart from this, exploit facets also for
precision in indexing (i.e. building complex expressions). Hence, the first
ones have only facets and the second one have both facets and roles attached
to them

Outside traditional KOS and in the spectrum of different so called
'faceted' vocabularies created to support browsing on portals the reasons
for
encoding facets is the same. These vocabularies do not attach any
'fundamental' meaning to the facets and yet they exploit them
to achieve certain functionality in managing terminology
and creating browsing/searching interface

>
> >       Mills/Broughton applied in BC2:
> >Thing/kind/part/property/material/process/operation/patient/product/by-
> >product/agent/space/time
>
> I'm not so happy about calling these "facets", because some of them
> depend on the role that something has rather than the fundamental
> category to which it belongs. This is a rule for citation order, in
> which I would say that the "thing" or "material" facets may occur more
> than once, as "thing", "material", "patient", "product" and "by-product"
> for example. Your other examples below are versions of this, or mixtures
> ASSOCIATED CONCEPTS FACET
> PHYSICAL ATTRIBUTES FACET
> STYLES AND PERIODS FACET
> AGENTS FACET
> ACTIVITIES FACET
> MATERIALS FACET
> OBJECTS FACET"
>
> This doesn't say anything about roles.


In order to have roles  one has to have data structure to which to
attach these roles (and later on the rules for processing the roles).

But the very fact that classification facets have their roles is *exactly*
the reason why
I would want to encode them for machine processing: I need to handle and
automate syntax. For processing pre-coordinate vocabularies it is very
important
to know that one concept belong to a certain facet as this context will
determine
its place in a string, its role and its meaning in this particular facet
as opposed to its meaning when it occurs in some other facet...
My understanding is that thesauri may as well 'pretend' that facets are
fundamental
categories of mutually exclusive terms and fix each term to occur only in
one facet
Thesauri have less need for disambiguation - because they are
zooming down on the narrow subject area where one concept has only one
broader concept
and often only one role. Such is the case of materials in AAT... where
stone or glass or leather is not discussed outside their role in the Art and
Architecture.

a) AAT, for instance,  does not have to accommodate 'marble deposits in
geology'
where the same concept may not be treated as 'material' .

b) thesauri do not need to use facets to
exercise the roles as they are used for single term indexing
(post-coordinate indexing)
They don't combine terms together in a complex expression.
[having said that: if one chose to produce composite terms with thesaurus,
one
would need to attach role to the facets_

Any analytico-synthetic classifications and other pre-coordinated indexing
langauges have to exploit facet analysis for more than one purpose. This
does not mean that facet in classification (Processes or Materials, Place)
in the context of a given discipline are not classes in which essential
properties are
exhibited by all its members.

(We can, for the purpose of this discussion, think of classification such as
Bliss 2
to be a collection of thesauri for instance)



aida
Received on Monday, 1 March 2004 08:55:55 GMT

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