The goal of this activity is to describe the sequence of interactions among the roles involved in each scenario. A Scenario describes how roles interact and coordinate to satisfy goals assigned to their organisation. Scenarios description occurs just after OID and IRI activities and at this stage is possible to assign to each requirement an organisation and a set of interacting behaviours (enacted by involved roles). The challenge is now describing how these different roles interact to realize the scenario.
Scenarios are deduced from the set of text descriptions of the system usage scenarios, and from the output of the OID and IRI activities.
Scenarios are described using an adapted version of UML sequence diagram. Each object in the diagram represents an AbstractRole, and we name it with the following syntax:< role name >:< organisation name >. The message in the sequence diagram may either denote an event generated by the external environment or an interaction/communication between roles. The meaning of this message will be later refined in the Agent Society Design Phase.
MAS MM Elements
Define(Scenario), Quote(Interaction), Quote(AbstractRole), Quote(Relate(AbstractRole, Interaction)).
Work to be done
A scenario description explores all the possible paths of an Organisation Identification diagram. A path describes a set of interacting roles working to achieve a required behaviour of the system. It is composed by interactions among roles of the same organisation identified during the IRI activity and interactions among roles of different organisations that have not been described yet. A role can appear in several scenarios. This activity is thus a way to verify that usage scenarios are effectively fulfilled. It also allows to check if the set of identified organisations is sufficient or not and to clearly describe the relationships among identified organisations. This last point will provide the initial elements in order to determine the future holonic structure of the system. A very close attention is paid to the interactions between Boundary Roles and the outside of the system. These interactions are based on the description of the actors and the part of the system designed with a classical object-oriented approach (like for instance GUIs, corporate DBMS wrappers and so on).
No specific guidelines have been identified for this activity. It resembles the classical scenario description activity of object-oriented design and the knowledge of the related techniques has been always sufficient in the conducted experiments. The only difference is in the slightly modified notation adopted for sequence diagrams.
A scenario associated to the Team Simulation Organisation is described in figure 12. Each role has of its own lifeline. The upper level is represented in this diagram via an actor called Team:Game Simulation. This scenario consists in the Team sending initialization messages. The StrategySelector then decides a strategy which is sent to the RoleAssigner which, in turn, decides of a role assignment and sends it to the Player. Robots are then situated on the field and the Player sends a ready-to-start message to the Team. The game begins when the user starts the match, the role Team then forward this information using the start message.
|Figure 12: Scenario of the Team Simulation Organisation |