Impure Simplicial Complexes: Complete Axiomatization

TL;DR

This paper develops a complete axiomatization for a logic that models message passing in synchronous systems with possible dead agents using impure simplicial complexes, advancing the understanding of distributed computing topology.

Contribution

It introduces a novel axiomatization for the logic of impure simplicial complexes and proves its soundness and completeness, including a new canonical model construction.

Findings

Axiomatization for impure simplicial complex logic established

Soundness and completeness of the logic proven

Canonical simplicial model construction introduced

Abstract

Combinatorial topology is used in distributed computing to model concurrency and asynchrony. The basic structure in combinatorial topology is the simplicial complex, a collection of subsets called simplices of a set of vertices, closed under containment. Pure simplicial complexes describe message passing in asynchronous systems where all processes (agents) are alive, whereas impure simplicial complexes describe message passing in synchronous systems where processes may be dead (have crashed). Properties of impure simplicial complexes can be described in a three-valued multi-agent epistemic logic where the third value represents formulae that are undefined, e.g., the knowledge and local propositions of dead agents. In this work we present an axiomatization for the logic of the class of impure complexes and show soundness and completeness. The completeness proof involves the novel construction of the canonical simplicial model and requires a careful manipulation of undefined formulae.