Annual rept. 1 Jul 80-30 Jun 81
CARNEGIE-MELLON UNIV PITTSBURGH PA
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In the first phase, the implementation of the FlexP parser was completed according to the design described in last years annual report, and was evaluated through use in a gracefully interacting interface. This application showed that FlexP was able to parse both grammatical and ungrammatical input according to a simple grammar of pattern-matching rewrite rules, that the bottom-up approach of FlexP was helpful in the case of ungrammatical input, and that a grammar suitable for use by FlexP could be defined in terms natural to the domain of interaction of the interface. However, the experimental use of FlexP also made it clear that FlexP had certain problems, largely due to the uniform nature of its grammar. In the second phase, the set of design choices on which FlexP was based was reviewed to determine if it was possible to resolve the problems that FlexP had without also losing the desirable aspects of its performance. This review led to the replacement of a single parsing strategy based on linear pattern matching with an approach based on multiple construction-specific parsing strategies. This approach was evaluated in a preliminary way through the construction of two small parsers, CASPAR and DYPAR, and was found to show considerable promise. Accordingly, design based on the same approach was begun for a more complete parser for restricted domain natural languages, and for a parser oriented towards an artificial command language of the type common in interactive user interfaces.