摘要:

In the following paper we analyze Reiter's default logic and suggest modifying the notion of an extension for default theories. This modification leads to two important properties which are not guaranteed in Reiter's formalism: the existence of extensions and semimonotonicity.

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1988.tb00086.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Logical omniscience may be described (roughly) as the state of affairs in which an agent explicitly believes anything which is logically entailed by that agent's beliefs. It is widely agreed that humans are not logically omniscient, and that an adequate formal model of belief, coupled with a correct semantic theory, would not entail logical omniscience. Recently, two prominent models of belief have emerged which purport both to avoid logical omniscience and to provide an intuitively appealing semantics. The first of these models is due to Levesque (1984b); the second to Fagin and Halpem (1985). It is argued herein that each of these models faces serious difficulties. Detailed criticisms are presented for each model, and a computationally oriented theory of intensions is presented which provides the foundation for a new formal model of belief. This formal model is presented in a decidable subset of first‐order logic and is shown to provide a solution to the general problem of logical omniscience. The model provides for the possibility of belief revision and places no a priori restrictions upon an agent's representation languag

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1988.tb00087.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The relative expressive power of a sentential operator □α is compared to that of a syntactical predicateL(‘α’) in the setting of first‐order logics. Despite well‐known results by Montague and by Thomason that claim otherwise, any of the so‐called “modal” logics of knowledge and belief can be compiled into classical first‐order logics that have a corresponding predicate on sentences. Moreover, through the use of a partial truth predicate, the standard modal axiom schemata can be translated into single sentences, making it possible to use conventional first‐order logic theorem provers to directly derive results in a wide

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1988.tb00088.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The Graph Theorist, GT, is a system that performs mathematical research in graph theory. From the definitions in its input knowledge base, GT constructs examples of mathematical concepts, conjectures and proves mathematical theorems about concepts, and discovers new concepts. Discovery is driven both by examples and by definitional form. The discovery processes construct a semantic net that links all of GT's concepts together.Each definition is an algebraic expression whose semantic interpretation is a stylized algorithm to generate a class of graphs correctly and completely. From a knowledge base of these concept definitions, GT is able to conjecture and prove such theorems as “The set of acyclic, connected graphs is precisely the set of trees” and “There is no odd‐regular graph on an odd number of vertices.” GT explores new concepts either to develop an area of knowledge or to link a newly acquired concept into a pre‐existing knowledge base. New concepts arise from the specialization of an existing concept, the generalization of an existing concept, and the merger of two or more existing concepts. From an initial knowledge base containing only the definition of “graph,” GT discovers such concepts as acyclic graphs, connected graphs, and b

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1988.tb00089.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0824-7935    

DOI:10.1111/j.1467-8640.1988.tb00085.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY