Progress report on automatic information retrieval

This study is a state-of-the-art report of work in automatic information retrieval. Various enhancements of operational on-line retrieval systems are described such as the utilization of special front-end devices providing compatibility among different search services, the introduction of fast back-end search devices, and the use of local clustering and query reformulation operations designed to improve retrieval output. Certain new algorithms for fast text matching and for optimum term weighting are also mentioned, as are advances in the construction of theoretical retrieval models.