Approximation of fuzzy context-free grammars
Fuzzy context-free max-star grammar (or FCFG(star), for short), as a straightforward extension of context-free grammar, has been introduced to express uncertainty, imprecision. and vagueness in natural language fragments. Li recently proposed the approximation of fuzzy finite automata, which may effectively deal with the practical problems of fuzziness, impreciseness and vagueness. In this paper, we further develop the approximation of fuzzy context-free grammars. In particular, we show that a fuzzy context-free grammar under max-star compositional inference can be approximated by some fuzzy context-free grammar under max-min compositional inference with any given accuracy. In addition, some related properties of fuzzy context-free grammars and fuzzy languages generated by them are studied. Finally, the sensitivity of fuzzy context-free grammars is also discussed. (c) 2009 Elsevier Inc. All rights reserved.
approximation fuzzy context-free grammars sensitivity fuzzy context-free languages equivalence