Concurrent Games with Multiple Topologies

TL;DR

This paper introduces Multi-Topology Games (MTGs), a new model for concurrent games with multiple possible topologies, and studies the existence of two types of Nash Equilibria, showing their decidability.

Contribution

The paper generalizes partial information games to Multi-Topology Games, defining two NE notions and proving their existence is decidable.

Findings

Decidability of Conservative NE existence

Decidability of Greedy NE existence

Introduction of MTGs as a new modeling framework

Abstract

Concurrent multi-player games with $\omega$-regular objectives are a standard model for systems that consist of several interacting components, each with its own objective. The standard solution concept for such games is Nash Equilibrium, which is a "stable" strategy profile for the players. In many settings, the system is not fully observable by the interacting components, e.g., due to internal variables. Then, the interaction is modelled by a partial information game. Unfortunately, the problem of whether a partial information game has an NE is not known to be decidable. A particular setting of partial information arises naturally when processes are assigned IDs by the system, but these IDs are not known to the processes. Then, the processes have full information about the state of the system, but are uncertain of the effect of their actions on the transitions. We generalize the setting above and introduce Multi-Topology Games (MTGs) -- concurrent games with several possible topologies, where the players do not know which topology is actually used. We show that extending the concept of NE to these games can take several forms. To this end, we propose two notions of NE: Conservative NE, in which a player deviates if she can strictly add topologies to her winning set, and Greedy NE, where she deviates if she can win in a previously-losing topology. We study the properties of these NE, and show that the problem of whether a game admits them is decidable.