| Z. Khasidashvili, M. Ogawa, V. van Oostrom, Perpetuality and uniform normalization in orthogonal rewrite systems, Inform. & Comput. 164 (1) (2001) 118151. |
....classical results in the study of uniform normalisation are: the I calculus is uniformly normalising [7, p. 20, 7 XXV] and non erasing steps are perpetual in orthogonal TRSs [14, Thm. II.5.9. 6] In previous work we have put these results and many variations on them in a unifying framework [13]. At the heart of that paper is the result (Thm. 3.16) that a term s not in normal form contains a redex which is external for any rewrite sequence from s. 1 The method presented here, is based instead on the existence of external redexes for a given sequence. This allows for generalisation of ....
....For ERSs and CRSs these results can be found as [12, Thm. 60] and [14, Cor. II.5.9.4] respectively. In this section the reader is assumed to be familiar with second order term rewrite systems be it in the form of combinatory reduction systems (CRSs [14] expression reduction systems (ERSs [13]) or higher order pattern rewrite systems (PRSs [17] We employ PRSs as de ned in op.cit. but will write x:s instead of x:s, thereby freeing the for usage as a function symbol. De nition 10. The order of a rewrite rule is the maximal order of the free variables in it. The order of a PRS ....
Z. Khasidashvili, M. Ogawa, and V. van Oostrom. Perpetuality and uniform normalization in orthogonal rewrite systems. I&C, To appear. http://www.phil.uu.nl/~oostrom/publication/ps/pun-icv2.ps.
....think that contracting only the S needed redexes of S needed families could yield S optimal reductions that are S minimal at the same time. We show however that this is not the case either in the # calculus or in OTRSs. Overview In the next section, we review Expression Reduction Systems [23, 24, 27]. In Section 3, we introduce the relative notion of neededness. In Section 4, we sketch some properties of our labelling system for OERSs needed to define a family relation among redexes. We prove correctness of the S needed strategy for computing terms of S, for all stable S, in Section 5, ....
....[42] and Aczel [1] Several interesting formalisms have been introduced later [24, 51, 36, 48] We refer to van Raamsdonk [49] for a survey. Expression Reduction Systems Here we use Expression Reduction Systems (ERSs) defined in [24] under the name of CRSs) The present formulation follows [27] and is simpler. Definition 1 Let # be an alphabet comprising variables x, y, z, function symbols, also called simple operators ; and operator signs or quantifier signs. Each function symbol has an arity k # N , and each operator sign # has an arity (m, n) with m,n #= 0 such that, for ....
[Article contains additional citation context not shown here]
Z. Khasidashvili, M. Ogawa, and V. van Oostrom. Perpetuality and uniform normalization in orthogonal rewrite systems. Information and Computation, To appear. Available from http://www.brl.ntt.co.jp/people/mizuhito/papers/ TRS.html.
....CERSs. In ERSs, orthogonality is defined as in CRSs [38,40] For conditional ERSs, we need also to require that descendants of redexes are redexes weakly similar to their ancestors, so that the admissible assignments are such that contraction of a redex cannot break down another redex [37] (for OERSs, this can easily be proven) To define descendants for CERS steps, we need to combine the descendant concepts for TRSs and for the calculus (or for S reduction rules) There are several different definitions of descendants both for TRSs and the calculus. For TRS steps, our definition ....
....contracted redex (x:s)t, its function part x:s, and the body s all have the contractum as the descendant, and the free occurrences of x in s descend to the corresponding substituted occurrences of t. This induces a descendant concept for S steps. For a precise definition of descendants we refer to [37]. Definition 4 A rewrite rule t s in a CERS R is left linear if t is linear (i.e. no metavariable occurs more than once in it) R is left linear if each rule in R is left linear. R is non ambiguous, or non overlapping, if an R redex u can properly contain an R redex v only in an argument, and ....
[Article contains additional citation context not shown here]
Z. Khasidashvili, M. Ogawa and V. van Oostrom, Perpetuality and uniform normalization in orthogonal rewrite systems, Information and Computation, in press. 38
No context found.
Z. Khasidashvili, M. Ogawa, V. van Oostrom, Perpetuality and uniform normalization in orthogonal rewrite systems, Inform. & Comput. 164 (1) (2001) 118151.
Online articles have much greater impact More about CiteSeer.IST Add search form to your site Submit documents Feedback
CiteSeer.IST - Copyright Penn State and NEC