Page 206 - DLIS402_INFORMATION_ANALYSIS_AND_REPACKAGING

Unit 11: Indexing Language: Types and Characteristics

Why do we need a thesaurus? Notes
One of the reasons for documenting our collections is that we wish to be able to find objects of a
particular kind. We may ask “What thermometers do we have in the collection?”, “What
arrowheads?”, “What frocks?”, “What whales?” or “What textile machinery?”
The simple answer is that we give each item a “name”, and then we can create a file of index cards,
or a computer file, in which we can search for these names and expect to find all the appropriate
items. This is the concept of the simple name field in the MDA data structure. It is straightforward
at first, and seems intuitive, but once you have documentation which has been built up over time,
perhaps by many different people, problems creep in unless there are rules and guidelines to maintain
consistency.
The word thesaurus is a rather fancy name, which has acquired a certain mystique, because it is
often bandied about as something necessary for effective information retrieval, but something which
sounds as though it will involve a lot of work. I have often heard curators say “That’s all very well
if you have the time and resources, but I have this great backlog of cataloguing to do, and would
never get through the half of it if I had to spend time setting up anything as complicated as a
thesaurus. What need is a simple list of names which I can use to index my objects.”
Main purpose in this paper is to make three points:
• A simple name list without some rules will rapidly become a mess.
• Only three simple rules are needed; using them will make life easier for you, not harder.
• So long as you stick to these rules, you can take an existing thesaurus and adapt it to your
needs; you are not limited to using the terms which are listed in it already, and you are not
obliged to use more detail than you need.
What are these rules?
1. Use a limited list of indexing terms, but plenty of entry terms
— link these with USE and USE FOR (UF) relationships.
2. Structure terms of the same type into hierarchies
— link these with BROADER TERM/NARROWER TERM (BT/NT) relationships.
3. Remind users of other terms to consider
— link these with RELATED TERM/RELATED TERM (RT/RT) relationships.
A limited list of indexing terms
A major purpose of a thesaurus is to match the terms brought to the system by an enquirer with the
terms used by the indexer. Whenever there are alternative names for a type of item, we have to
choose one to use for indexing, and provide an entry under each of the others saying what the
preferred term is. If we index all full-length ladies’ garments as dresses, then someone who searches
for frocks must be told that they should look for dresses instead.
This is no problem if the two words are really synonyms, and even if they do differ slightly in
meaning it may still be preferable to choose one and index everything under that. I do not know the
difference between dresses and frocks but I am fairly sure that someone searching a modern clothing
collection who was interested in the one would also want to see what had been indexed under the
other. We normally do this by linking the terms with the terms USE and USE FOR, thus:
Dresses USE FOR Frocks
Frocks USE Dresses
This may be shown in a printed list, or it may be held in a computer system, which can make the
substitution automatically. If an indexer assigns the term Frocks, the computer will change it to
Dresses, and if someone searches for Frocks the computer will search for Dresses instead, so that

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