Defining an interface for Agents, AbstractAgent, that can be sent Messages; implementing Agent that implements AbstractAgent, is a specialized Unit, and is also a MessageHandler; implementing a wrapper for Agent implementations, AgentHandle, which decouples the interface defined by AbstractAgent from the actual implementation, that is now the class Agent; specializing the System interface as MessagingSystem, that consists of Agents rather than plain Units and can send Messages to those Agents; adding a simple implementation of MessagingSystem in the Core library as MessagingSystemImpl, which turns Messages into direct MessageHandler invocations; adding a new example, messaging-system, showcasing the main features of MessagingSystem and Agents.