978 - 1 - 107 - 01417 - 6 - Unification Grammars

Natural languages1 are among Nature’s most extraordinary phenomena. While humans acquire language naturally and use it with great ease, the formalization of language, which is the focus of research in linguistics, remains evasive. As in other sciences, attempts at formalization involve idealization: ignoring exceptions, defining fragments, and the like. In the second half of the twentieth century, the field of linguistics has undergone a revolution: The themes that are studied, the vocabulary with which they are expressed, and the methods and techniques for investigating them have changed dramatically. While the traditional aims of linguistic research have been the description of particular languages (both synchronically and diachronically), sometimes with respect to other, related languages, modern theoretical linguistics seeks the universal principles that underlie all natural languages; it is looking for structural generalizations that hold across languages, as well as across various phrase types in a single language, and it attempts to delimit the class of possible natural languages by formal means. The revolution in linguistics, which is attributed mainly to Noam Chomsky, has influenced the young field of computer science. With the onset of programming languages, research in computer science began to explore different kinds of languages: formal languages that are constructed as a product of concise, rigorous rules. The pioneering work of Chomsky provided the means for applying the results obtained in the study of natural languages to the investigation of formal languages. One of the earliest areas of study in computer science was human cognitive processes, in particular natural languages. This area of research is