TAILIEUCHUNG - Báo cáo khoa học: "A THREE-VALUED FEATURE INTERPRETATION OF NEGATION STRUCTURE DESCRIPTIONS"

Feature structures are informational elements that have been used in several linguistic theories and in computational systems for natural-language processing. A logicaJ calculus has been developed and used as a description language for feature structures. In the present work, a framework in three-valued logic is suggested for defining the semantics of a feature structure description language, allowing for a more complete set of logical operators. In particular, the semantics of the negation and implication operators are examined. Various proposed interpretations of negation and implication are compared within the suggested framework. . | A THREE-VALUED INTERPRETATION OF NEGATION IN FEATURE STRUCTURE DESCRIPTIONS Anuj Dawar Dept of Comp and Info. Science University of Pennsylvania Philadelphia PA 19104 K. Vijay-Shanker Dept of Comp and Info. Science University of Delaware Newark DE 19716 April 20 1989 ABSTRACT Feature structures are informational elements that have been used in several linguistic theories and in computational systems for natural-language processing. A logical calculus has been developed and used as a description language for feature structures. In the present work a framework in three-valued logic is suggested for defining the semantics of a feature structure description language allowing for a more complete set of logical operators. In particular the semantics of the negation and implication operators are examined. Various proposed interpretations of negation and implication are compared within the suggested framework. One particular interpretation of the description language with a negation operator is described and its computational aspects studied. 1 Introduction and Background A number of linguistic theories and computational approaches to parsing natural language have employed the notion of associating informational elements called feature structures consisting of features and their values with phrases. Rounds and Kasper KR86 RK86 developed a logical calculus that serves as a description language for these structures. Several researchers have expressed a need for extending this logic to include the operators of negation and implication. Various interpretations have been suggested that define a semantics for these operators see Section but none has gained universal acceptance. In Per87 Pereira set forth certain properties that any such interpretation should satisfy. In this paper we present an extended logical calculus with a semantics in three-valued logic based on Kleene s three-valued logic Kle52 that includes an interpretation of negation motivated by the approach given

• Báo cáo khoa học
• A THREE VALUED FEATURE INTERPRETATION
• NEGATION STRUCTURE DESCRIPTIONS
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