Irrespective of their subject matter or information needs, searchers of both databases normally began with a brief query consisting of two terms. This appears typical for end users of any information retrieval system, whether based on Boolean or best-match ranking principles [11]. Since searchers are unable for whatever reason to generate more query terms at the outset, the ENQUIRE system provided support for query enhancement by automatically mapping query terms with the thesaurus in order to: a) add preferred terms to the query automatically, b) display other thesaurus terms which the user could add to the query, c) allow the user to further explore the thesaurus structure by navigating from the displayed thesaural terms.
The possibility of assigning higher weights to preferred terms occurring in the initial query was considered but not implemented in the current project. The effectiveness of adding such terms has not yet been analysed but it is assumed that they are unlikely to be detrimental. The main problem still seems to be to persuade users to take up the thesaurus options provided. Earlier studies have shown that they find it difficult to assess the merits of suggested thesaural terms before examining the initial results of a search, and this was confirmed in the first ENQUIRE formative evaluation. As a result, the interface for the final tests displayed the partially matching ``suggested words'' at the same time as the documents from the first search, thus reducing their potential take-up, and, even more, the likelihood that users would make the effort to carry out explicit thesaurus navigation.