Wiring the Pi-calculus to Denotational Semantics
For researchers in concurrency theory and semantics, this work provides a novel connection between pi-calculus and denotational semantics, though it is incremental in extending existing categorical frameworks.
The paper introduces AWpi, a dialect of the Asynchronous pi-calculus where wires behave as substitutions, enabling a categorical structure for denotational semantics. It constructs a relative Seely category, bridging operational pi-calculus with denotational models.
We introduce a dialect of the Asynchronous pi-calculus, called AWpi, in which (1) an input name may be owned, at any time, by at most one process; (2) each name has either only the input or only the output capability. As a result, special processes called wires (aka forwarders, that is, processes that receive values at one name and re-transmit) behave as substitutions when composed with any AWpi process. Thus AWpi naturally yields a category, whose morphisms are AWpi processes (modulo the reference behavioural equivalence, barbed congruence) and whose objects are types; and where wires act as identity morphisms. We show that the category of processes can be further organised into (sub)categories with the structures needed for the interpretation of common higher-order language features in the literature by drawing on insights from game semantics; notably, we construct a relative Seely category, the categorical structure that concurrent game semantics has. At the same time, AWpi follows the tradition of ordinary pi-calculi in that expressiveness is preserved and the operational and algebraic theory are developed in a similar manner, notwithstanding substantial technical differences in their development and proofs. In short, the goal of AWpi is to remain faithful to the operational and algebraic tradition of the pi-calculi while connecting to the tradition of denotational models for programming languages.