Comparison of Upward and Downward Generalizations in CF-Induction
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CF-induction is a sound and complete procedure for finding hypotheses in full clausal theories. It is based on the principle of Inverse Entailment (IE), and consists of two procedures: construction of a bridge theory and generalization of it. There are two possible ways to realize the generalization task in CF-induction. One uses a single deductive operator, called γ-operator, and the other uses a recently proposed form of inverse subsumption. Whereas both are known to retain the completeness of CF-induction, their logical relationship and empirical features have not been clarified yet. In this paper, we show their equivalence property and clarify the difference on their search strategies, which often leads to significant features on their obtained hypotheses.
Keywordsinverse entailment CF-induction generalization inverse subsumption γ-operator
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