If the Parser Fails

The unforgiving nature of natural language components when someone uses an unexpected input has recently been a concern of several projects. For instance, Carbonell (1979) discusses inferring the meaning of new words. Hendrix, e t .a l . (1978) describe a system that provides a means for naive users to define personalized paraphrases and that l i s ts the items expected next at a point where the parser blocks. Weischedel, e t .a l . (1978) show how to relax both syntactic and semantic constraints such that some classes of ungrammatical or semantically inappropriate input are understood. Kwasny aod Sondheimer (1979) present techniques for understanding several classes of syntactically il l-formed input. Codd, e t .a l . (1978) and Lebowitz (1979) present alternatives to top-down, le f t to r igh t parsers as a means of dealing with some of these problems.