A graph-theoretic approach to default logic
Information and Computation
The complexity of default reasoning under the stationary fixed point semantics
Information and Computation
Is intractability of nonmonotonic reasoning a real drawback?
Artificial Intelligence
Artificial Intelligence
Default reasoning from conditional knowledge bases: complexity and tractable cases
Artificial Intelligence
Tractable Reasoning in Artificial Intelligence
Tractable Reasoning in Artificial Intelligence
Reasoning with Incomplete Information
Reasoning with Incomplete Information
Propositional Logic: Deduction and Algorithms
Propositional Logic: Deduction and Algorithms
IJCAI '99 Proceedings of the Sixteenth International Joint Conference on Artificial Intelligence
Model Checking for Nonmonotonic Logics: Algorithms and Complexity
IJCAI '99 Proceedings of the Sixteenth International Joint Conference on Artificial Intelligence
Complexity results for restricted credulous default reasoning
AI Communications
Complexity Results for 2CNF Default Theories
Fundamenta Informaticae
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In this paper, the class of regular disjunction-free default theories is introduced and investigated. A transformation from regular default theories to normal default theories is established. The initial theory and the transformed theory have the same extensions when restricted to old variables. Hence, regular default theories enjoy some similar properties (e.g., existence of extensions, semi-monotonicity) as normal default theories. Then, a new algorithm for credulous reasoning of regular theories is developed. This algorithm runs in a time not more than O(1.45n), where n is the number of defaults. In case of regular prerequisite-free or semi-2CNF default theories, the credulous reasoning can be solved in polynomial time. However, credulous reasoning for semi-Horn default theories is shown to be NP-complete although it is tractable for Horn default theories. Moreover, skeptical reasoning for regular unary default theories is co-NP-complete.