When semantic preference rules were applied to the semantic lexicon, the number of entries with multiple semantic types was reduced to 423 (1.5 percent). Of those lexemes in the corpus that had semantic types, 3,474 (12.6 percent) had two or more types.
This suggests that the Specialist Lexicon has about 79 percent coverage for syntactic information and 38 percent coverage for semantic information for discharge summaries. Matching the Specialist Lexicon against one year's worth of discharge summaries identified 27,633 distinct lexical forms, 13,322 of which had at least one semantic type. Results: Matching the Specialist Lexicon against the Metathesaurus produced a semantic lexicon with 75,711 lexical forms, 22,805 (30.1 percent) of which had two or more semantic types. Based on this evidence, semantic preference rules were developed to reduce the number of lexemes with multiple semantic types.
A concordance program was used to find contrasting contexts for each lexeme that would reflect different semantic senses. Lexical items with multiple semantic types were examined to determine whether some of the types could be eliminated, on the basis of usage in discharge summaries. The semantic lexicon was then used to assign semantic types to lexemes occurring in a corpus of discharge summaries (603,306 sentences). This yielded a “semantic lexicon,” in which each lexeme is associated with one or more syntactic types, each of which can have one or more semantic types. Objective: Construction of a resource that provides semantic information about words and phrases to facilitate the computer processing of medical narrative.ĭesign: Lexemes (words and word phrases) in the Specialist Lexicon were matched against strings in the 1997 Metathesaurus of the Unified Medical Language System (UMLS) developed by the National Library of Medicine.
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