Towards a Self-Extending Lexicon

Towards a Self-Extending Lexicon* Uri Zernik Michael G. Dyer Artificial Intelligence Laboratory Computer Science Department 3531 Boelt~r Hall University of tMifomis Los Angeles, California 90024 Abstract The problem of manually modifying the lexicon appears with any natural language processing program. Ideally, a program should be able to acquire new lexieal entries from context, the way people learn. We address the problem of acquiring entire phrases, specifically Jigurative phr~es, through augmenting a phr~al lezico~ Facilitating such a self-extending lexicon involves (a) disambiguation~se|ection of the intended phrase from a set of matching phrases, (b) robust parsin~-comprehension of partially-matching phrases, and (c) error analysis---use of errors in forming hy- potheses about new phrases. We have designed and im- plemented a program called RINA which uses demons to implement funetional-~rammar principles. RINA receives new figurative phrases in context and through the appli- cation of a sequence of failure-driven rules, creates and refines both the patterns and the concepts which hold syntactic and semantic information about phrases. David vs. Goliath Native: Learner: Native: Learner: Native: Learner: Native: Remember the s~ory of David and Goliath? David took on Goliath. David took GoltLth sons,here? No. David took on Goliath. He took on him. He yon the fight? No. He took him on. David attacked him. He ~ok him on. He accepted She challenge? Right. Native: Learner: Here in annt,her story. John took on the third exam question. He took on a hard problem. Another dialogue involves put one's foot do~-a. Again, the phrase is unknown while its constituents are known: Going Punk 1. Introduction A language understanding program should be able to acquire new lexical items from context, forming for novel phrases their linguistic patterns and figuring out their conceptual meanings. The lexicon of a learning program should satisfy three requirements: Each lexical entry should (1) be learnable, (2) facilitate conceptual analysis, and (3) facilitate generation. In this paper we focus on the first two aspects. 1.1 The Task Domain Two examples, which will be used throughout this paper, are given below. In the first dialogue the learner is introduced to an unknown phrase: take on. The words take and on are familiar to the learner, who also remembers the biblical story of David and Goliath. The program, modeling a language learner, interacts with a native speaker, as follows: * This work w~s made possible in part by s grant from the Keck Foundation. Native: Learner: Native: Learner: Jenny vant,ed ~o go punk, but, her father put, his toot dovu. He moved his foot dora? It, doen not, mike sense. No. He put his foot, dora. He put his foot dovu. He refused to let her go punk. A figurative phrase such as put one's fooc down is a linguistic pattern whose associated meaning cannot be produced from the composition of its constituents. Indeed, an interpretation of the phrase based on the meanings of its constituents often exists, but it carries a different meaning. The fact that this literal interpreta- tion of the figurative phrase exists is …

Content truncated to 500 words