  FASTUS is a system for extracting information from natural language text for
entry into a database and for other applications. It works essentially as a
cascaded, nondeterministic finite-state automaton. There are five stages in the
operation of FASTUS. In Stage 1, names and other fixed form expressions are
recognized. In Stage 2, basic noun groups, verb groups, and prepositions and
some other particles are recognized. In Stage 3, certain complex noun groups
and verb groups are constructed. Patterns for events of interest are identified
in Stage 4 and corresponding ``event structures'' are built. In Stage 5,
distinct event structures that describe the same event are identified and
merged, and these are used in generating database entries. This decomposition
of language processing enables the system to do exactly the right amount of
domain-independent syntax, so that domain-dependent semantic and pragmatic
processing can be applied to the right larger-scale structures. FASTUS is very
efficient and effective, and has been used successfully in a number of
applications.
