On the consistency of Koomen's fair abstraction rule

Abstract

We construct a graph model for ACP,, the algebra of communicating processes w%h silent steps, in which Koomen’s Fair Abstraction Rule (KFAR) holds, and also versions of the Approximation Induction Principle (AIP) and the Recursive Definition & Specification Principles (RDP&RSP). We use this model to prove that in ACP, (but not in ACP!) each computably recursively definable process is finitely recursively definable.