tailieunhanh - Báo cáo khoa học: "COMPUTATIONAL SEMANTICS"

Although the formalisms normally used for describing the semantics of natural languages are far from computationally tractable, it is possible to isolate particular semantic phenomena and interpret them within simpler formal systems. Quantified mass noun phrases is one such part. We describe a simple formal system suitable for the interpretation of quantified mass noun phrases. The main issue of this paper is to develop an algorithm for deciding the validity of sentences in the formal system and hence for deciding the validity of natural language inferences where all the involved noun phrases are quantified mass noun phrases. The. | COMPUTATIONAL SEMANTICS OF MASS TERMS Jan Tore L0nning Department of Mathematics University of Oslo . Box 1053 Blindem 0316 Oslo 3 Norway ABSTRACT Although the formalisms normally used for describing the semantics of natural languages are far from computationally ttactable it is possible to isolate particular semantic phenomena and interpret them within simpler formal systems. Quantified mass noun phrases is one such part. We describe a simple formal system suitable for the interpretation of quantified mass noun phrases. The main issue of this paper is to develop an algorithm for deciding the validity of sentences in the formal system and hence for deciding the validity of natural language inferences where all the involved noun phrases are quantified mass noun phrases. The decision procedure is based on a tableau calculus. INTRODUCTION A formal semantics for a part of a natural language attempts to describe the truth conditions for sentences or propositions expressed by sentences in model theoretic terms and thereby also the relation of valid inferences between sentences. From the point of view of computational linguistics and natural language understanding it is important whether this relation of entailment can be made computational. In general the question must be answered in the negative. All proposed formal semantics of say English are at least as complex as first order logic and hence at best semi-decidable which means that ư a sentence p is a logical consequence of a set of sentences E then there exists a proof for p from s but no effective way to find such a proof. Several proposals use even more complex logics like the higher order intensional logic used in Montague grammar which has no deductive theory at all. We will not oppose to the view that English incorporates at least the power of first order logic and that even more complex formalisms may be needed to represent the meaning of all aspects of English. But we believe there are two different .