Abstract:
An evaluation test was made of an experimental data-base prepared
by the Space Documentation Service of the European Space Agency,
consisting of some 44,000 items from NASA STAR for 1973 and
1974. With this data-base it was possible to search on natural
language terms in the titles and abstracts, in addition to the normal
searches on controlled language index terms. The on-line searches were
carried out at four centres, each centre being responsible for ten
questions, with two searches in the alternative search modes being made
by different people for each question. Up to twenty-five documents
retrieved in the two searches for each question were sent to the
originator of the question for relevance assessment.
The results are presented in a number of different ways, but in every
case the natural language searches showed a significantly higher recall
ratio than the controlled language, with little difference in the precision
ratios. It is suggested that the main reason for the superiority of
natural language searching is the greater exhaustivity of the abstracts
as compared to the indexing.
