Evolution of software challenges multi-agent systems to be adaptive and the adaptation capabilities should be provided at both the agent level and the system level. In this paper, we study the adaptation of multi-agent systems from the system level and describe a formal framework for multi-agent systems with adaptation capabilities. In the framework, agents are indirectly inter-connected via roles and interaction protocols are defined as entities independent of agents and roles. Thus agents, roles, and interaction protocols involved in multi-agent systems need not always adjust their behaviors or specifications to adapt to the changes of system structures and interaction protocols.