Meta-rules as a basis for processing ill-formed input

  • Authors:
  • Ralph M. Weischedel;Norman K. Sondheimer

  • Affiliations:
  • University of Delaware, Newark, DE;USC/Information Sciences Institute, Marina del Rey, CA

  • Venue:
  • Computational Linguistics - Special issue on ill-formed input
  • Year:
  • 1983

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Abstract

If natural language processing systems are ever to achieve natural, cooperative behavior, they must be able to process input that is ill-formed lexically, syntactically, semantically, or pragmatically. Systems must be able to partially understand, or at least give specific, appropriate error messages, when input does not correspond to their model of language and of context.We propose meta-rules and a control structure under which they are invoked as a framework for processing ill-formed input. The left-hand side of a meta-rule diagnoses a problem as a violated rule of normal processing. The right-hand side relaxes the violated rule and states how processing may be resumed, if at all.Examples discussed in the paper include violated grammatical tests, omitted articles, homonyms, spelling/typographical errors, unknown words, violated selection restrictions, personification, and metonymy. An implementation of a meta-rule processor within the framework of an augmented transition network parser is also described.