Page 213 - DLIS402_INFORMATION_ANALYSIS_AND_REPACKAGING

Information Analysis and Repackaging

Notes

In the thesaurus, BT/NT relationships can be used for parts and wholes in only
four special cases: parts of the body, places, disciplines and hierarchical social
structures.

Polyhierarchies

As shown in the sample thesaurus above, a term can have several broader terms, if it belongs to
several broader categories. The thesaurus is then said to be polyhierarchical. Cardigans, for example,
are simultaneously Knitwear and Jackets, and should be retrieved whenever either of these categories
is being searched for.
With a polyhierarchical thesaurus it would take more space to repeat full hierarchies under each of
several broader terms in a printed version, but this can be overcome by using references, as
ROOT does. There is no difficulty in displaying polyhierarchies in a computerised version of a
thesaurus.
Use of a thesaurus when cataloguing
A thesaurus is an essential tool which must be at hand when indexing a collection of objects, whether
by writing catalogue cards by hand or by entering details directly into a computer. The general
principles to be followed are:
• Consider whether a searcher will be able to retrieve the item by a combination of the terms
you allocate.
• Use as many terms as are needed to provide required access points.
• If you allocate a specific term, do not also allocate that term’s broader terms.
• Make sure that you include terms to express what the object is, irrespective of what it might
have been used for.
If you have a computerised thesaurus, with good software, this can give you a lot of direct help.
Ideally it should provide pop-up windows displaying thesaurus terms which the cataloguer can
choose from and then “paste” directly into the catalogue record without re-typing.
It should be possible to browse around the thesaurus, following its chain of relationships or
displaying tree structures, without having to exit the current catalogue record, and non-preferred
terms should automatically be replaced by their preferred equivalents. A cataloguer should be able
to “force” new terms onto the thesaurus, flagged for review later by the thesaurus editor. When
editing thesaurus relationships, reciprocals should be maintained automatically, and it should not
be possible to create inconsistent structures.
Use and modification of existing thesauri
As there are many thesauri in existence already, it is worth considering seriously whether one of
these can be used before embarking on the job of creating a new one for a particular museum or
collection. So long as the general principles are followed, you should be able to expand a thesaurus
to give you more detail if you need it, or truncate some sections at a high level if they contain more
detail than your collections justify. So long as the relationships are universally true, it should be
possible to combine sections of thesauri developed by different museums and thus avoid duplication
of work.
Even when using an authoritative thesaurus, some care is needed, and I have mentioned some
limitations of ROOT and AAT in 7.1 and 7.4 above. It is still much easier to base your work on
something like these than to build your own from scratch, unless you have a much specialised
collection.

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