Actor modeling consists of identifying and analyzing both the actors of the environment and the system’s actors and agents. In particular, in the early requirement phase actor modeling focuses on modeling the stakeholders and their intentions as social actors which want to achieve goals.

During late requirement, actor modeling focuses on the definition of the system-to be actor, whereas in architectural design, it focuses on the structure of the system to- be actor specifying it in terms of sub-systems (actors), interconnected through data and control flows. In detailed design, the system’s agents are defined specifying all the notions required by the target implementation platform, and finally, during the implementation phase actor modeling corresponds to the agent coding.

 See The Tropos metamodel and its use for more information.