tailieunhanh - Báo cáo khoa học: "AUTOMATIC ACQUISITION OF THE LEXICAL SEMANTICS OF VERBS FROM SENTENCE FRAMES*"

This paper presents a computational model of verb acquisition which uses what we will callthe principle of structured overeommitment to eliminate the need for negative evidence. The learner escapes from the need to be told that certain possibilities cannot occur ( "ungrammatical") by one simple expedient: It assumes that all properties it has observed are either obligatory or forbidden until it sees otherwise, at which point it decides that what it thought was either obligatory or forbidden is merely optional. This model is built upon a classificationof verbs based upon a simple three-valued set of features which represents. | AUTOMATIC ACQUISITION OF THE LEXICAL SEMANTICS OF VERBS FROM SENTENCE FRAMES Mort Webster and Mitch Marcus Department of Computer and Information Science University of Pennsylvania 200 s. 33rd Street Philadelphia PA 19104 ABSTRACT This paper presents a computational model of verb acquisition which uses what we will call the principle of structured overcommitment to eliminate the need for negative evidence. The learner escapes from the need to be told that certain possibilities cannot occur . are ungrammatical by one simple expedient It assumes that all properties it has observed are either obligatory or forbidden until it sees otherwise at which point it decides that what it thought was either obligatory or forbidden is merely optional. This model is built upon a classification of verbs based upon a simple three-valued set of features which represents key aspects of a verb s syntactic structure its predicate argument structure and the mapping between them. 1 INTRODUCTION The problem of how language is learned is perhaps the most difficult puzzle in language understanding. It is necessary to understand learning in X order to understand how people use and organize language. To build truly robust natural language systems we must ultimately understand how to enable our systems to learn new forms themselves. Consider the problem of learning new lexical items in context. To take a specific example how is it that a child can learn the difference between the verbs look and see inspired by Landau and Gleitman 1985 They clearly have similar core meanings namely perceive by sight . One initially attractive and widely-held hypothesis is that This work was partially supported by the DARPA grant N00014-85-K0018 and ARO grant DAA29-84- 0027. The authors also wish to thank Beth Levin and the anonymous reviewers of this paper for many helpful comments. We also benefited greatly from discussion of issues of verb acquisition in children with Lila Gleitman. word meaning is learned