We present a coinductive framework for defining infinitary analogues of equational reasoning and rewriting in a uniform way. We define the relation 1=, a hitherto unknown notion of infinitary equational reasoning, and !1, the standard notion of infinitary rewriting as follows: 1= := R. (=E [ R) !1 := μR. S. (!R [ R)  S where μ and  are the least and greatest fixed-point operators, respectively, and where R := { hf(s1, . . . , sn), f(t1, . . . , tn)i | f 2 , s1 R t1, . . . , sn R tn } [ Id . The setup captures rewrite sequences of arbitrary ordinal length, but it has neither the need for ordinals nor for metric convergence. This makes the framework especially suitable for formalizations in theorem provers.
Schloss Dagstuhl - Leibniz Center of Informatics
doi.org/10.4230
Leibniz International Proceedings in Informatics
International Conference on Rewriting Techniques and Applications
Computer Security

Endrullis, J., Hansen, H., Hendriks, D., Polonsky, A., & Silva, A. (2015). A Coinductive Treatment of Infinitary Term Rewriting and Equational Reasoning. In Proceedings of International Conference on Rewriting Techniques and Applications 2015 (RTA) (pp. 143–159). Schloss Dagstuhl - Leibniz Center of Informatics. doi:10.4230