Controlled index terms, own free-text
search terms and keywords
Örebro University Library
Birgitta Hansson and Monica Norr
Index terms
Selecting the right search terms is essential if you want good search
results.
Most databases use index terms that describe the content of its
documents. The same document may be found in several different
databases and have different index terms linked to them depending
on the content of the database.
The terms are listed in what is normally labelled as a thesaurus,
which is a directory of the controlled index terms in that specific
database.
Many databases have a comprehensive thesaurus. If so, the
thesaurus is a good place to start your search. Other databases
provide a more simple list of index terms, or do not have one at all. If
that is the case, you need to identify your own search terms and
perform free-text searches.
Definition of thesaurus
thesaurus storehouse, from Greek thēsauros ’treasure’
(oxforddictionaries.com)
In the thesaurus, the index terms are listed hierarchically
from broader to more narrow concepts. There are also
references to help you identify the right search term. It
might also contain hints for related search terms.
The index terms are referred to as descriptors, subjects,
MeSH terms or IEEE terms, for example.
Advantages when using the database’s
controlled index terms via thesaurus
• Articles on the same topic are linked to the same index
terms which facilitates your search and increases your
chances at finding the articles published on the topic.
• In a thesaurus, you will be given hints and tips helping you
to identify wider, more general index terms as well as index
terms that are more narrow and more specific.
• Possibility to identify related terms.
Hints for searches using controlled index
terms
• Find a relevant article and check the controlled index terms
that have been defined for the article.
• Find these in the database thesaurus and review both
the wider and more narrow index terms that are
displayed.
• Check the related index terms.
• Read the explanations linked to the index term which
are provided in many databases.
• Perform the search directly via the thesaurus.
a) Own free-text search terms
Own free-text search terms will pick up all articles with the
entered search term in, for instance, the title, the name of the
journal, the article summary, or in the name of the publishers.
The search terms may appear in several places, for example
once in the title and once in the summary. Generally, the
search does not cover the full article.
Searches using controlled index terms or own search terms
generate different results. For example, leadership as a
controlled index term in the ERIC database gives 11 000
references whereas the same term used in a free-text search
provides 56 000 references. Searches using the controlled
index terms generate a higher degree of subject-specific hits.
b) Own free-text search terms
Phrase search
When searching using a term that contains more than one word it might be a
good idea to put the words in quotation marks. This indicates that you want
to do a search on the words as a phrase, i.e. that they should appear
together. This means that you avoid getting hits where the words appear
separately in different places in a text (e.g. “public sector”).
Truncation (word-stem search)
Using truncation with an asterisk (*) allows you to expand your search so
that you get a hit on all search terms with the same word stem but with
different suffixes. The word stem creat* will for instance generate hits for
create, creation, creator, creature, creatine etc.
See search methods
Advantages when using own search terms
• For picking up as much information as possible at the start of a search.
Among the articles that are generated, you can identify the ones that
are relevant to your search and find the controlled index terms for these.
The controlled index terms can in turn be used in a new, more specific
and more narrow search.
• New concepts that have not yet been introduced as controlled index
terms.
• New articles entered into the database but for which controlled index
terms have not yet been defined.
• As a finalising complement in searches where the controlled index
terms do not limit the search results sufficiently.
Keywords
There is no uniform standard as to how keywords are used in
databases and author’s instructions.
In some cases they are defined by the author once an article has been
finalised and is about to be submitted for publication in a journal
(author keywords).
Often, journals have their own guidelines with respect to keywords. In
some journals, authors are asked to pick controlled index terms from a
database within the subject area in question.
Each database provides information and help texts on whether, and if
so how, keywords are used.
Tips
Film (2:55) “How (and Why) to use the APA Thesaurus
When Searching PsycINFO…” (general example from
PsycINFO).