Effective Automatic Indexing Using Term Addition and Deletion

In mformaUon retrieval indexing is the task consisting of the assignment to stored records and mcommg mformatton requests of content ~dent~fiers capable of representing record or query content If the mdexmg is performed automatically and the records are wntten documents, an mmal set of index terms might be chosen by taking words extracted from document roles or abstracts, this mmal term assignment might then be improved by addmg related terms chosen from a thesaurus, by deletmg extraneous or marginal terms, and by replacing smgle terms by term combmaaons and phrases. In the present study formal proofs are given of the retrieval effectiveness under well-defined condmons of mdexmg policies based on the use of single terms, term additions and deletions, and term combmaaons or phrases.