Gemini Natural-Language Understanding System

Natural-language research under SRI International's project on Improved Spoken-Language Understanding is focused on the development of Gemini, a natural-language parsing and semantic interpretation system based on unification grammar. "Unification grammar" means that grammatical categories incorporate features that can be assigned values; so that when grammatical category expressions are matched in the course of parsing or semantic interpretation, the information contained in the features is combined, and if the feature values are incompatible the match fails.

Gemini applies a set of syntactic and semantic grammar rules to a word string using a bottom-up parser to generate a logical form, which is a structured representation of the context-independent meaning of the string. Gemini can be used with a variety of grammars. We have developed both a general English grammar, used in the ATIS system, and an application-specific grammar for the CommandTalk system.

Optional modules in Gemini provide robustness through a novel technique for detecting and correcting speech repairs, and by heuristically combining interpretations of grammatical fragments into an overall interpretation for the utterance, in cases where the Gemini grammar and lexicon do not provide a single complete analysis. Gemini has also been used as part of a language model to increase speech recognition accuracy. Recently we have developed software to compile Gemini grammars into context-free grammars that can be directly used as language models in the Nuance speech recognizer (a commercially available system based on SRI-developed technology). For more information on Gemini, see