Migration of a Chosen Architectural Pattern to Service Oriented ...

Chapter 3. Architectural Patterns 47Client 1Node 1Client 2BrokerNode 2Client 3Figure 3.9: Example usage of Broker patternregistered Controllers. It also cooperates with View because Model cannotify View about changes of state of Model. View interacts with Controllerbecause View invokes Controller. It can also retrieve data fromModel.Controller interacts with both Controller and Model (see figure 3.10)6. Presentation Abstraction ControllerOverview– the purpose of the pattern is similar to the purpose of MVCpattern. This pattern represents different approach to the problem of interactionof a user with an application.ElementsAgent– each agent consist of three elements: Presentation which is meantto provide information to a user, Abstraction manipulating data of thesystem and Controller handling communication between Presentation andAbstraction. Agents are further divided into agents representing particularfunctionalities and agents coordinating the system.Layer of Abstraction– an application consists of several Layers of Abstraction.Each layer contains Agent on the same level of abstraction. The toplayer contains only one agent which coordinates the whole application whilethe “leaves agents” in the lowest layer represent particular functionalities.A layer invokes other layer on behalf of an agent.Relationships– Each Agent can communicate directly with other agentsin the same layer of abstraction. Layers of Abstraction communicate onlywith layers bellow (see figure 3.11).