Abstract: A hybrid natural language understanding (NLU) system which is particularly designed for processing natural language text. Primary functional components of the NLU system include a preprocessor; a word look-up and morphology module which communicates with a lexicon and a learning module; a syntactic parser which interfaces with an augmented transition network (ATN) grammar; a case frame applier, which converts the syntactic structure into canonical, semantic "case frames"; and a discourse analysis component which integrates explicit and implied information in the text into a conceptual structure which represents its meaning. This structure may be passed on to a knowledge based system, data base, to interested analysts or decision makers, etc. Significant feedback points are provided, e.g., the case frame applier may notify the syntactic parser of a semantically incorrect parse, or the syntactic parser may seek a semantic judgment based on a fragmentary parse.