Language learning from membership queries and characteristic examples

Abstract

This paper introduces the notion of characteristic examples and shows that the notion contributes to language learning in polynomial time. A characteristic example of a language L is an element of L which includes, in a sense, sufficient information to represent L. Every context-free language can be divided into a finite number of languages each of which has a characteristic example and it is decidable whether or not a context-free language has a characteristic example. We present an algorithm that learns parenthesis languages using membership queries and characteristic examples. Our algorithm runs in time polynomial in the number of production rules of a minimal parenthesis grammar and in the length of the longest characteristic example.