Introduction to the Special Issue on Finite-State Methods in NLP

The idea for this special issue came up during the preparations of the International Workshop on Finite-State Methods in Natural Language Processing, that was held at Bilkent University in Ankara, Turkey in the summer of 1998. The number of the submissions had exceeded our initial expectations and we were able to select quite a good set of papers from those submitted. Further, the workshop and the preceding tutorial by Kenneth Beesley, on finite-state methods, was attended by quite a large number of participants. This led us to believe that interest in the theory and applications of finitestate machinery was alive and well, and that some of the papers from this workshop along with further additional submissions could make a very good special issue for this journal. The five papers in this issue are the result of this process. The last decade has seen a quite a substantial surge in the use of finite-state methods in all aspects of natural language applications. Fueled by the theoretical contributions of Kaplan and Kay (1994), Mohri’s recent contributions on the use of finite-state techniques in various NLP problems (Mohri 1996, 1997), the success of finite-state approaches especially in computational morphology, for example, Koskenniemi (1983), Karttunen (1983), and Karttunen, Kaplan, and Zaenen (1992), and, finally, the availability of state-of-the-art tools for building and manipulating large-scale finite-state systems (Karttunen 1993; Karttunen and Beesley 1992; Karttunen et al. 1996; Mohri, Pereira, and Riley 1998; van Noord 1999), recent years have seen many successful applications of finite-state approaches in tagging, spell checking, information extraction, parsing, speech recognition, and text-to-speech applications. This is a remarkable comeback considering that in the dawn of modern linguistics (Chomsky 1957), finitestate grammars were dismissed as fundamentally inadequate. As a result, most of the work in computational linguistics in the past few decades has been focused on far more powerful formalisms. Recent publications on finite-state technology include two collections of papers (Roche and Schabes 1997; Kornai 1999) with contributions covering a wide range of these topics. This special issue, we hope, will add to these contributions. The five papers in this collection cover many aspects of finite-state theory and applications. The papers Treatment of Epsilon Moves in Subset Construction by van Noord and Incremental Construction of Minimal Acyclic Finite-State Automata and Transducers by Daciuk, Watson, Watson, and Mihov, address two fundamental aspects in the construction of finite-state recognizers. Van Noord presents results for various methods for producing a deterministic automaton with no epsilon transitions from a nondeterministic automaton with a large number of epsilon transitions, especially those resulting from finite-state approximations of context-free and more powerful formalisms. Daciuk et al. present a new method for constructing minimal, deterministic, acyclic