CREATING AND EVALUATING ENTRY TERMS

An indexing language is made more accessible to searchers and indexers by the presence of entry terms or near‐synonyms. This paper first presents an evaluation of existing entry terms and then presents and tests a strategy for creating entry terms. The key tools in the evaluation of the entry terms are documents already indexed into the Medical Subject Headings (MeSH) and an automatic indexer. If the automatic indexer can better map the title to the index terms with the use of entry terms than without entry terms, then the entry terms have helped. Sensitive assessment of the automatic indexer requires the introduction of measures of conceptual closeness between the computer and human output. With the tools described in this paper, one can systematically demonstrate that certain entry terms have ambiguous meanings. In the selection of new entry terms another controlled vocabulary or thesaurus, called the Systematized Nomenclature of Medicine (SNOMED), was consulted. An algorithm for mapping terms from SNOMED to MeSH was implemented and evaluated with the automatic indexer. The new SNOMED‐based entry terms did not help indexing but did show how new concepts might be identified which would constitute meaningful amendments to MeSH. Finally, an improved algorithm for combining two thesauri was applied to the Computing Reviews Classification Structure (CRCS) and MeSH. CRCS plus MeSH supported better indexing than did MeSH alone.