Browsing by Author "Polat, F."
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Item Open Access Distributed conflict resolution among cooperating expert systems(Wiley-Blackwell Publishing, 1993-11) Polat, F.; Shekhar, S.; Guvenir, H. A.Cooperating experts approach attempts to integrate and coordinate the activities of multiple specialised problem solvers that come together to solve complex tasks such as design, medical diagnosis, business management and so on. Due to the different goals, knowledge and viewpoints of agents, conflicts may arise at any phase of the problem-solving process. Managing diverse expertise requires well-organised models of conflict resolution. In this paper, a model for cooperating experts is described which openly supports multi-agent conflict detection and resolution. The model is based on the idea that each agent has its own conflict knowledge which is separated from its domain level knowledge, and each agent has its own conflict resolution knowledge which is not accessible and known by others. Furthermore, there are no globally known conflict resolution strategies. Each agent involved in a conflict chooses a resolution scheme according to its self interest. The model is described by using an example in the domain of office design and it is compared with other systems.Item Open Access A negotiation platform for cooperating multi-agent systems(Sage Publications Ltd., 1993-05-23) Polat, F.; Shekhar, S.; Guvenir, H. A.Distributed artificial intelligence attempts to integrate and coordinate the activities of multiple, intelligent problem solvers that come together to solve complex tasks in domains such as design, medical diagnosis, business management, and so on Due to the different goals, knowledge, and viewpoint of the agents, conflicts might arise at any phase of the problem-solving process. Managing diverse knowledge requires well-organized models of conflict resolution. In this paper, a system for cooperating intelligent agents which openly supports multiagent conflict detection and resolution is described. The system is based on the insights, first, that each agent has its own conflict knowledge which is separated from its domain-level knowledge; and, second, that each agent has its own conflict management knowledge which is not accessible to or known by others. Furthermore, there are no globally-known conflict-resolution strategies. Each agent involved in a conflict chooses a resolution scheme according to its self interest. The problem-solving environment allows a new problem solver to be added, or an existing one to be removed, without requiring any modification of the rest of the system, and therefore achieves open information system semantics.Item Open Access Reusability and schema evolution in object - oriented query models(ASME, New York, NY, United States, 1996) Polat, F.; Alhajj, R.In this paper, we have benefited from having an object algebra maintaining closure that makes it possible to have the output from a query persistent in the hierarchy. Based on this, it is possible to maximize reusability in object-oriented databases. Furthermore, we show how the object algebra is utilized to handle basic schema evolution functions without requiring any special set of built-in functions to serve the purpose. The invariants and the conflict resolving rules are specified. It is also shown how other schema functions are derivable from the basic ones.Item Open Access Unification-based approach for knowledge base verification(1991) Polat, F.; Guvenir, H. A.Knowledge base verification, a part of the validation process in expert system development, includes checking the knowledge base for completeness and consistency to guard against a variety of errors that can arise during the process of transferring expertise from a human expert to a computer system. Regardless of how an expert system is developed, its developers can profit from a systematic check of the knowledge base without gathering extensive data for test runs, even before the full reasoning mechanism is functioning. Until recently knowledge base verification has been largely ignored, which has led to expert systems with knowledge base errors and no safety factors for correctness. We propose a unification-based approach for verification of a knowledge base represented in the form of production rules and facts. This approach can determine conflicting, redundant, subsumed and circular rules; redundant if-conditions in rules; dead-end rules; and cycles and contradiction in rules.Item Open Access UVT: a unification based tool for knowledge based verification(IEEE, 1993) Polat, F.; Guvenir, H. A.A method for verifying knowledge bases that is based on the unification of rules is discussed. One characteristic that distinguishes this approach from other verification tools is that it infers some of the rules that are not explicitly given in the rule base and considers their effect on the verification process. The method can determine conflicting, redundant, subsumed, circular, and dead-end rules, redundant if conditions in rules, and cycles and contradictions within rules. The method has been implemented in a computer program called UVT (for unification-based verification tool) and tested on sample knowledge bases.Item Open Access View maintenance in object-oriented databases(Springer, 1996-09) Alhajj, Reda; Polat, F.in this paper, we present a model that facilitates view maintenance within object-oriented databases. For that purpose, we differentiate between two categories of classes, base classes and brother classes. While the former constitute the actual database, the latter are introduced to hold virtual database, i.e., views derived from base classes. To achieve incremental view update, we introduce a modification list into each base class. A series of algorithms are developed to serve the purpose. Finally it happened that, view maintenance within object-oriented databases subsumes that within the nested and hence conventional relational models.