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Let G be the set of finite graphs whose vertices belong to some fixed countable set, and let ≡ be an equivalence relation on G. By the strengthening of ≡ we mean an equivalence relation ≡s such that The most important case that we study in this paper concerns equivalence relations defined by graph properties. We write G ≡ Φ H, where Φ is a graph property(More)
We propose and study algorithms to compute minimal models, stable models and answer sets of t-CNF theories, and normal and disjunctive t-programs. We are especially interested in algorithms with non-trivial worst-case performance bounds. The bulk of the paper is concerned with the classes of 2-and 3-CNF theories, and normal and disjunctive 2-and 3-programs,(More)