Philip R. Cohen

The adaptive agent architecture: achieving fault-tolerance using persistent broker teams

Brokered multi-agent systems can be incapacitated and rendered non-functional when the brokers become inaccessible due to failures that can occur in any distributed software system. We propose that the theory of teamwork can be used to specify robust brokered architectures that can recover from broker failures, and we present the adaptive agent architecture (AAA) to show the feasibility of this approach. The previous teamwork theory based on joint intentions assumes that team members remain in a team as long as the team exists. We extend this theory to allow dynamic broker teams whose members can change with time. We also introduce a theory of restorative maintenance goals that enables the brokers in an AAA broker team to start new brokers and recruit them to the broker team. As a result, an AAA-based multi-agent system can maintain a specified number of functional brokers in the system despite broker failures, thus effectively becoming a self-healing system.

TORUS: A step towards bridging the gap between data bases and the casual user

Abstract This paper describes TORUS, a natural language understanding system that serves as a front end to a data base management system in order to facilitate communication with casual users. The system employs a semantic network to store knowledge about a data base of student files. This knowledge is used to find the meaning of each input statement, to decide what action to take with respect to the data base, and to select information that must be output in response to the input statement. A prototype version of TORUS has been implemented.

An integration of two language understanding methodologies

This paper describes an attempt at integrating two existing methodologies to form a natural language understanding system, and at evaluating 1.PAK, an AI language developed at the University of Toronto. The design of this prototype version is based upon Fillmores case grammar representation and Charniaks scheme for organizing routines to update a semantic network memory. Two essential components of such a system, an English parser and generation routine, have been developed separately and are not covered here, apart from describing their interfaces with the rest of the system. The system performs semantic disambiguation and deduction via demons and base routines, as in Charniaks thesis. Simple question-answering facilities are also available and planned extensions to this facility will encompass the consequent theorem methodology of PLANNER.