Approximating Context-Free Grammars with a Finite-State Calculus

Although adequate models of human language for syntactic analysis and semantic interpretation are of at least contextfree complexity, for applications such as speech processing in which speed is important finite-state models are often preferred. These requirements may be reconciled by using the more complex grammar to automatically derive a finite-state approximation which can then be used as a filter to guide speech recognition or to reject many hypotheses at an early stage of processing. A method is presented here for calculating such finite-state approximations from context-free grammars. It is essentially different from the algorithm introduced by Pereira and Wright (1991; 1996), is faster in some cases, and has the advantage of being open-ended and adaptable. 1 Finite-state approximations Adequate models of human language for syntactic analysis and semantic interpretation are typically of context-free complexity or beyond. Indeed, Prolog-style definite clause grammars (DCGs) and ...

• Type: Conference
• Year: 1997
• Where: ACL
• Authors: Edmund Grimley-Evans
• Keywords: ACL 1997, ACL 2007, Finite-state Approximations, Important Finite-state Models, Speech Recognition