Task Assignment

Abstract

Task assignment in multi-agent systems is a complex coordination problem, in particular in systems that are subject to dynamic and changing operating conditions. To enable agents to deal with dynamism and change, adaptive task assignment approaches are needed. In this chapter, we study two approaches for adaptive task assignment that are characteristic for two classical families of coordination mechanisms for task assignment. In particular, we study and compare a field-based approach for task assignment (FiTA) with a protocol-based approach (DynCNET). In FiTA, tasks emit computational fields in a virtual environment that attract idle agents. Agents follow the gradient of the combined field that guides them toward tasks. DynCNET is an extension of the well-known contract net protocol CNET [151], with “Dyn” referring to support for dynamic task assignment. Both FiTA and DynCNET enable task assignment in the system based on local interaction among agents and allow for adaptation of task assignment during delayed commencement. Yet, the approaches differ in the manner agents realize task assignment. In FiTA, agents use simple rules that guide them toward tasks, providing an emergent solution for task assignment. Contrarily, in DynCNET agents use explicit selection mechanisms and can negotiate about task assignment. Our focus is on systems with homogeneous tasks that can be executed by individual agents. We do not consider complex tasks, for instance composite tasks that have to be divided among agents, or a combination of related tasks that have to be executed by a single agent. This perspective allows us to focus on the basic challenges of task assignment in systems that are subject to dynamic and changing operating conditions.