Task Specification

At this step, for each agent we focus on its behavior in order to decomposing it into tasks. Tasks generally encapsulate some functionality that forms a logical unit of work. For every agent in the model, we draw an activity diagram that is made up of two swimlanes. The one from the right-hand side contains a collection of activities symbolizing the agent’s tasks, whereas the one from the left-hand side contains some activities representing the other interacting agents.

The Task Specification diagram of the PurchaseManager agent

A Task Specification diagram (see previous figure) summarizes what the agent is capable of doing, ignoring information about roles that an agent plays when carrying out particular tasks. Relationships between activities signify either messages between tasks and other interacting agents or communication between tasks of the same agent. The last are not speech acts, but rather signals addressing the necessity of beginning an elaboration, that is triggering a task execution or delegating another task to do something. Each activity may be further specified by sequence diagrams, activities diagrams or semi-formal text with fields for preconditions, triggers, etc. In order to yield an agent’s T.Sp. diagram we need to look at all of the agent’s R.Id. diagrams (i.e. all of the scenarios it participates to). We then explore all of the interactions and internal actions that the agent performs to accomplish a scenario’s purpose. From each R.Id. diagram we obtain a collection of related tasks. Grouping them all together appropriately then results in the T.Sp. diagram.

Because drawing a Task Specification diagram for each agent would require much space in the paper, we only depict the one for the PurchaseManager agent. A Listener task is needed in order to pass incoming communication to the proper task. Further tasks are needed to handle all the incoming messages of the R. Id. scenario (see ReceivePurchaseRequest and ReceiveDeliveryNotification tasks in the previous figure that correspond to the R. Id messages coming from the PurchaseMonitor and StoreUI agents respectively, see the previous phase diagram). Likewise, a task is introduced for each outgoing message of the R. Id. scenario (see AskForAdvice, AskNegotiation, AskOrdering, UpdatePurchaseHistory, NotifyEndOfPurchase). Also, extra tasks may be introduced to face with a better decomposition of the agent (see StartPurchase task).

 

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