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Abstract : |
The following theorem of Huet and L'evy forms the basis of all results on optimal reduction strategies for orthogonal term rewriting systems: every term not in normal form contains a needed redex, and repeated contraction of needed redexes results in the normal form, if the term under consideration has one. We generalize this theorem to computations to root-stable form and we argue that the resulting notion of root-neededness is more fundamental than (other variants of) neededness when it comes to infinitary normalization. 1, |