Assumption-Commitment Types for Resource Management in Virtually Timed Ambients

Abstract

This paper introduces a type system for resource management in the context of nested virtualization. With nested virtualization, virtual machines compete with other processes for the resources of their host environment in order to provision their own processes, which could again be virtual machines. The calculus of virtually timed ambients formalizes such resource provisioning, extending the capabilities of mobile ambients to model the dynamic creation, migration, and destruction of virtual machines. The proposed type system is compositional as it uses assumptions about the outside of a virtually timed ambient to guarantee resource provisioning on the inside. We prove subject reduction and progress for well-typed virtually timed ambients, expressing that upper bounds on resource needs are preserved by reduction and that processes do not run out of resources.