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DigiCULT 29
with online catalogues and Web search systems. Many
existing KOS have been published and made avail-
able for Web-based access. However, they tend not
to be fully integrated into indexing and search sys-
tems. Their interfaces are typically primarily designed
for display purposes and are not appropriate for
direct programmatic access. The lack of any standard-
ised application programming interface (API) hinders
attempts at interoperability.
In this case study, we first briefly introduce one
particular KOS, the thesaurus, together with the fac-
eted approach to KOS design. We then describe the
FACET Project which investigated the potential of
faceted thesauri in retrieval and reflect on some of
our experiences during the project. We finish by dis-
cussing some key concerns for realising the poten-
tial of thesauri in Web-based systems, particularly the
issue of access protocols.
T
HESAURI
T
he thesaurus is one of the most commonly used
controlled vocabulary indexing tools in muse-
ums.
8
It is a type of KOS structured by a core set of
semantic relationships which are specified by inter-
national standards (BS5723, ISO2788, ANSI/NISO
Z39.19).
Hierarchical relationships as illustrated in Figure
1 structure broader (more general) and narrower
(more specific) concepts in relation to a given con-
cept, and allow a thesaurus to be visualised as a
series of concept hierarchies. Associative relationships
describe somewhat looser connections between con-
cepts. Equivalence relationships specify terms that
can be considered as effective synonyms for a con-
cept, according to the scope and objectives of a par-
ticular thesaurus. Thus a major thesaurus will typically
include a large entry vocabulary a network of lin-
guistic equivalents, colloquial terms and synonyms
which can be used to channel searchers towards the
formal controlled vocabulary indexing terms (`pre-
ferred' terms, determined by established literary war-
rant). Used in this way the entry vocabulary acts as
an effective mediation device, educating users about
the nature and terminology of the search domain and
providing direct links to terms actually used in index-
ing. Scope notes, used in conjunction with any evi-
dence provided by the relationship structure, assist
in the disambiguation of thesaurus terms. They also
communicate the limits of the context within which
a given term may be applied.
F
ACETED
A
PPROACH
M
any people recommend a faceted approach
to thesaurus (and related KOS) design. For
example, the AAT is a large thesaurus (about 125,000
terms), organised into seven facets (and 33 hierarchies
as subdivisions) according to semantic role: Associ-
ated concepts, Physical attributes, Styles and periods,
Agents, Activities, Materials, Objects and optional fac-
ets for time and place. According to the AAT online
Web pages,
9
Hierarchical relation-
ships (BT/NT)
Associative relation-
ships (RT)
burnishing (polishing)
BT
polishing
NT
ball burnishing
Processes and Techniques
. finishing (process)
. . polishing
. . . burnishing (polishing)
. . . . ball burnishing
. . . electropolishing
burnishing (polishing)
RT
burnishers
(metalworkers)
RT
flat burnishers
RT
polishing irons
RT
tooth burnishers
burnishers (metalworkers)
RT
burnishing
(polishing)
Equivalence relation-
ships (UF/USE)
Scope notes (SN)
burnishing (polishing)
UF
burnished
(polished)
burnished (polished)
USE
burnishing
(polishing)
burnishing (polishing)
SN
Making shiny or
lustrous by
rubbing with
a tool that com-
pacts or smooths
burnishing (photography)
SN
Method of ob-
taining a glossy
surface on col-
lodion prints
by pressing them
between rollers
Figure 1: Examples of thesaurus structure from
the Getty Art & Architecture Thesaurus
8
Willpower Information:
Thesaurus principles and
practice, http://www.
willpower.demon.co.uk/
thesprin.htm
9
Getty: Art & Architecture
Thesaurus On Line, http://
www.getty.edu/research/
conducting_research/
vocabularies/aat/about.html