The CASA architecture describes a platform for the provisioning of services by agents by supporting three levels of agent design. At the base level is a framework to build an agent out of reusable components. Using this framework, a predefined component structure realises control mechanisms for reactive, deliberative, and interactive behaviour. The agent communication used for interactions is guided by protocols and formal service descriptions. By these concepts, CASA provides an open, scalable agent architecture for service provisioning. Keywords agent architectures, component systems, agent-based service provisioning, multi-agent collaboration, communication protocols