Determining the extent of lookahead in syntactic error repair

Abstract

Many syntactic error repair strategies examine several additional symbols of input to guide the choice of a repair; a problem is determining how many symbols to examine. The goal of gathering all relevant information is discussed and shown to be impractical; instead we can gather all information relevant to choosing among a set of “minimal repairs.” We show that finding symbols with the property “Moderate Phrase-Level Uniqueness” is sufficient to establish that all information relevant to these minimal repairs has been seen. Empirical results on the occurrence of such symbols in Pascal are presented.