Yet Another Chart-Based Technique for Parsing Ill-Formed Input

A new chart-based technique for parsing ill-formed input is proposed. This can process sentences with unknown/misspelled words, omitted words or extraneous words. This generalized parsing strategy is, similar to Mellish's, based on an active chart parser, and shares the many advantages of Mellish's technique. It is based on pure syntactic knowledge, it is independent of all grammars, and it does not slow down the original parsing operation if there is no ill-formedness. However, unlike Mellish's technique, it doesn't employ any complicated heuristic parameters. There are two key points. First, instead of using a unified or interleaved process for finding errors and correcting them, we separate the initial error detection stage from the other stages and adopt a version of bi-directional parsing. This effectively prunes the search space. Second, it employs normal top-down parsing, in which each parsing state reflects the global context, instead of topdown chart parsing. This enables the technique to determine the global plausibility of candidates easily, based on an admissible A search. The proposed strategy could enumerate all possible minimal-penalty solutions in just 4 times the time taken to parse the correct sentences.