tailieunhanh - Báo cáo khoa học: "A Computational Semantics for Natural Language"

In the new Head-driven Phrase Structure G r a m m a r (HPSG) language processing system that is currently under development at Hewlett-Packard Laboratories, the Montagovian semantics of the earlier GPSG system (see [Gawron et al. 19821) is replaced by a radically different approach with a number of distinct advantages. In place of the lambda calculus and standard first-order logic, our medium of conceptual representation is a new logical forrealism called NFLT (Neo-Fregean Language of Thought); compositional semantics is effected, not by schematic lambda expressions, but by LISP procedures that operate on NFLT expressions to produce new expressions | A Computational Semantics for Natural Language Lewis G. Creary and Carl J. Pollard Hewlett-Packard Laboratories 1501 Page Mill Road Palo Alto CA 94304 USA Abstract In the new Head-driven Phrase Structure Grammar HPSG language processing system that is currently under development at Hewlett-Packard Laboratories the Montagovian semantics of the earlier GPSG system see Gawron et al. 1982 is replaced by a radically different approach with a number of distinct advantages. In place of the lambda calculus and standard first-order logic our medium of conceptual representation is a new logical formalism called NFLT Neo-Fregean Language of Thought compositional semantics is effected not by schematic lambda expressions but by LISP procedures that operate on NFLT expressions to produce new expressions. NFLT has a number of features that make it well-suited for natural language translations including predicates of variable arity in which explicitly marked situational roles supercede order-coded argument positions sortally restricted quantification a compositional but nonextensional semantics that handles causal contexts and a principled conceptual raising mechanism that we expect to lead to a computationally tractable account of propositional attitudes. The use of semantically compositional LISP procedures in place of lambda-schemas allows US to produce fully reduced translations on the fly with no need for post-processing. This approach should simplify the task of using semantic information such as sortal incompatibilities to eliminate bad parse paths. 1. Introduction Someone who knows a natural language is able to use utterances of certain types to give and receive information about the world. How can we explain this We take as our point of departure the assumption that members of a language community share a certain mental system a grammar that mediates the correspondence between utterance types and other things in the world such as individuals relations and states of .