Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
The documentation of (unbounded-len~h) copying and cross-serial constructions in a few languages in the recent literature is usually taken to mean that natural languages are slightly context-sensitive. However, this ignores those copying constructions which, while productive, cannot be easily shown to apply to infinite sublanguages. To allow such finite copying constructions to be taken into account in formal modeling, it is necessary to recognize that natural languages cannot be realistically represented by formal languages of the usual sort. Rather, they must be modeled as families of formal languages or as formal languages with indefinite vocabularies. Once this is done,. | COPYING IN NATURAL LANGUAGES CONTEXT-FREENESS AND QUEUE GRAMMARS Alexis Manaster-Ramer University of Michigan 2236 Fuller Road 108 Ann Arbor MI 48105 ABSTRACT The documentation of unbounded-length copying and cross-serial constructions in a few languages in the recent literature is usually taken to mean that natural languages are slightly context-sensitive. However this ignores those copying constructions which while productive cannot be easily shown to apply to infinite sublanguages. To allow such finite copying constructions to be taken into account in formal modeling it is necessary to recognize that natural languages cannot be realistically represented by formal languages of the usual sort. Rather they must be modeled as families of formal languages or as formal languages with indefinite vocabularies. Once this is done we see copying as a truly pervasive and fundamental process in human language. Furthermore the absence of mirror-image constructions in human languages means that it is not enough to extend Context-free Grammars in the direction of context-sensitivity. Instead a class of grammars must be found which handles context-sensitive copying but not context-free mirror images. This suggests that human linguistic processes use queues rather than stacks making imperative the development of a hierarchy of Queue Grammars as a counterweight to the Chomsky Grammars. A simple class of Context-free Queue Grammars is introduced and discussed. Introduction The claim that at least some human languages cannot be described by a Context-free Grammar no matter how large or complex has had an interesting career. In the late 1960 s it might have seemed given the arguments of Bar-Hillel and Shamir 1960 about respectively coordinations in English Postal 1964 about reduplication-cum-incorporation of object noun stems in Mohawk and Chomsky 1963 about English comparative deletion that this claim was firmly established. Potentially serious and at any rate embarrassing-problems
