A note on a term rewriting characterization of PTIME
نویسندگان
چکیده
In [2] a clever term rewriting characterization of the polytime functions is given by de ning a set RB′ of feasible rewrite rules for predicative recursion. It is shown that the derivation length function (DlRB′ ,f ) of RB′ for f is bounded by a monotone polynomial in the length of the inputs. We give a simpli ed proof of this result. As a consequence we obtain the stronger result that DlRB′ ,f is bounded by a monotone polynomial in the length of the normal inputs, only. Thereby the speci c features of RB′ are more accurately expressed. We believe our results imply the usefulness of so-called Cichon's principle (CP) to the (worst-case) derivation length analysis of a given term rewriting system R.
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تاریخ انتشار 2004