During this phase we are concerned with an agent’s externally visible behavior, so any representation of its internal behavior is approximate. In PASSI a role is defined by the set of responsibilities defining the subjective behavior of an agent in an interaction (conversation) with another or in providing some service in one or more scenarios; an agent may play one or more roles at the same time.
Because of the interaction that is behind any conversation or service provided, the role can be regarded as a social manifestation of the agent behavior.
The Roles Identification phase produces a set of sequence diagrams that specify scenarios from the agents’ identification use case diagram. In this context, it is particularly important to investigate all the paths involving inter-agent communications, and fortunately some guidelines can be considered: (1) such communication paths are shown in the A.Id. diagram by the presence of a relationship between two agents with the communication/instantiation stereotype; (2) each relationship may belong to several scenarios; (3) for each relationship in a specific scenario of the A.Id. diagram, there is at least one message in the sequence diagram of the R.Id. phase.
In this phase, roles are identified in the sense that agents’ external manifestations are captured in sequence diagrams where agents participate playing one or more roles concurring to the evolution of the system dynamic.
The different roles that an agent can play are introduced as objects in the appropriate sequence diagram. An agent may participate in several scenarios playing distinct roles in each, and may even appear more than once in a single sequence diagram playing different roles.
An example of the Role Identification Diagram is depicted in the next figure:
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