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ON CLOSED WORLD DATA BASES / 119

Classics (Collection 2)

ON CLOSED WORLD DATA BASES Raymond Reiter The University of British Columbia Vancouver, British Columbia ABSTRACT Deductive question-answering systems generally evaluate queries under one of two possible assumptions which we in this paper refer to as the open and closed world assumptions. The open world assumption corresponds to the usual first order approach to query evaluation: Given a data base DB and a query Q, the only answers to Q are those which obtain from proofs of Q given DB as hypotheses. Under the closed world assumption, certain answers are admitted as a result of failure to find a proof. More specifically, if no proof of a positive ground literal exists, then the negation of that literal is assumed true. In this paper, we show that closed world evaluation of an arbitrary query may be reduced to open world evaluation of socalled atomic queries.


11 Theorem-Proving by Resolution as a Basis for Question-Answering Systems

Classics (Collection 2)

This paper shows how a question-answering system can be constructed using first-order logic as its language and a resolution-type theorem-prover as its deductive mechanism. A working computer-program, Q A3, based on these ideas is described. The performance of the program compares favorably with several other general question-answering systems. A question-answering system accepts information about some subject areas and answers questions by utilizing this information. The type of questionanswering system considered in this paper is ideally one having the following features: 1.


On closed world data bases

Classics

ON CLOSED WORLD DATA BASES Raymond Reiter The University of British Columbia Vancouver, British Columbia ABSTRACT Deductive question-answering systems generally evaluate queries under one of two possible assumptions which we in this paper refer to as the open and closed world assumptions. The open world assumption corresponds to the usual first order approach to query evaluation: Given a data base DB and a query Q, the only answers to Q are those which obtain from proofs of Q given DB as hypotheses. Under the closed world assumption, certain answers are admitted as a result of failure to find a proof. More specifically, if no proof of a positive ground literal exists, then the negation of that literal is assumed true. In this paper, we show that closed world evaluation of an arbitrary query may be reduced to open world evaluation of socalled atomic queries.




Steps Toward Automatic Theory Formation

Classics

This paper describes a theory formation system which can discover a partial axiomization of a data base represented as extensionally defined binary relations.- The system first discovers all possible intensional definitions of each binary relation in terms of the others. It then determines a minimal set of these relations from which the others can be defined. It then attempts to discover all the ways the relations of this minimal set can interact with each other, thus generating a set of inference rules. Although the system was originally designed to explore automatic techniques for theory construction for question-answering systems, it is currently being expanded to function as a symbiotic system to help social scientists explore certain kinds of data bases.In IJCAI-73: THIRD INTERNATIONAL JOINT CONFERENCE ON ARTIFICIAL INTELLIGENCE, 20-23 August 1973, Stanford University Stanford, California.


A net structure for semantic information storage, deduction and retrieval

Classics

This paper describes a data structure, MENS (MEmory Net Structure), that is useful for storing semantic information stemming from a natural language, and a system, MENTAL (MEmory Net That Answers and Learns) that interacts with a user (human or program), stores information into and retrieves information from MENS and interprets some information in MENS as rules telling it how to deduce new information from what is already stored. MENTAL can be used as a guestion-answering system with formatted input/output, as a vehicle for experimenting with various theories of semantic structures or as the memory management portion of a natural language question-answering system.See also:U. Wisconsin Technical Report 109 versionScanned, non-OCR, versionIn IJCAI-71: INTERNATIONAL JOINT CONFERENCE ON ARTIFICIAL INTELLIGENCE. British Computer Society, London, pp. 512-523.


User's guide to QA3

Classics

A question-answering system. Tech. Note 15, AI Group, Stanford Research Institute, Menlo Park, Calif.