Recovery Strategies for Parsing Extragrammatical Language

Practical natural language interfaces must exhibit robust behaviour in the presence of extragrammatical user input. This paper classifies different types of grammatical deviations and related phenomena at the lexical, sentential and dialogue levels and presents recovery strategies tailored to specific phenomena in the classification. Such strategies constitute a tool chest of computationally tractable methods for coping with extragrammaticality in restricted domain natural language. Some of the strategies have been tested and proven viable in existing parsers.