FINITE-STATE TRANSDUCTION OF RELATED WORD FORMS FOR TEXT INDEXING AND RETRIEVAL

The present invention solves a number of problems in using stems (canonical indicators of word meanings) in full-text retrieval of natural language documents, and thus permits recall to be improved without sacrificing precision. It uses various arrangements of finite-state transducers to accurately encode a number of desirable ways of mapping back and forth between words and stems, taking into account both systematic aspects of a language's morphological rule system and also the word-by-word irregularities that also occur. The techniques described apply generally across the languages of the world and are not just limited to simple suffixing languages like English. Although the resulting transducers can have many states and transitions or arcs, they can be compacted by finite-state compression algorithms so that they can be used effectively in resource-limited applications. The invention contemplates the information retrieval system comprising the novel finite state transducer as a database and a processor for responding to user queries, for searching the database, and for outputting proper responses, if they exist, as well as the novel database used in such a system and methods for constructing the novel database.