Curtis H.K. Tsang, Clarence S.W. Lau and Y.K. Leung Object-Oriented Technology From Diagram to Code with Visual Paradigm for UML Curtis H.K. Tsang, Clarence S.W. Lau and Y.K. Leung McGraw-Hill Education (Asia), 2005 Dr. Hussein Al-Zoubi

Tricks and Tips Creating Cohesive and Self-sufficient Subsystems Subsystems may be considered as the next level of abstraction down from the entire system. Ideally, a subsystem should be a cohesive and independent part of the complex system, so as to bring out the benefits of portability, reusability and maintainability. A cohesive and independent subsystem is loosely coupled with other subsystems, and data coupling is the most loosely-coupled communication method between entities. Refining Class Diagrams Using MVC-level Scenario Analysis

Tricks and Tips (cont’d)

Tricks and Tips (cont’d)

Tricks and Tips (cont’d)

Tricks and Tips (cont’d) Understanding System Reusability for Different Types of Objects Type of Object Application Scope Reusability Object library General purpose Any application Entity Class Domain Specific Within the domain Control Class Application Specific Within the application Boundary Class

Tricks and Tips (cont’d) Do Not Create Giant Control Objects Because control objects are application specific, if they are given too much intelligence or logic, they will not be reusable for other applications. Responsibilities to be assigned to a control object: the control sequence of messages in the scenario; information about the sessions in relation to the use case scenario, e.g. session ID, session status, etc.; control logic of the run-time session, e.g. transaction management, error recovery, etc.

Tricks and Tips (cont’d) Checking Consistency between Use Case and Sequence Diagrams

Tricks and Tips (cont’d) Identifying Objects and Operations through Scenario Analysis Boundary and control objects can be identified by walking through the flow of events of a use case scenario Each entry of the flow of events involves three steps: The actor inputs some information into the system The system performs some actions The system responds to the actor’s input

Tricks and Tips (cont’d) The following guidelines can help quickly identify the boundary and entity objects in the use case scenario: Identify boundary objects by asking questions such as: “what input device(s) would be required for the actor(s) to enter the information?”, “what output device(s) would be required for the system to give a response to the actors?” Identify entity objects by asking questions such as: “ what information is required to respond to the actors input?”

View Alignment between Sequence Diagram and State Diagram

Developing Statechart Diagrams for Control Objects Statechart diagram of the Card Controller