Object-Oriented Design Chapters 10, 11 Object-Oriented Design Classes Objects SD DCD

Revision: Study pages 13 – 20 from study-guide: Answer the 12 questions on page 20!

Introduction: Object-oriented analysis models were discussed in Chapters 2 - 5 Chapter 10, the fundamental principles: A complete coverage of design principles and skills to at least do basic object-oriented design Chapter 11 presents more advanced concepts particularly for detailed design with use case realizations: enhanced detailed design skills, and concepts related to design patterns, which are critically important for programming.

Foundation: Object-oriented design is a process by which a set of detailed object-oriented design models are built and then used by the programmers to write and test the new system. One of the strengths of the object-oriented approach is that the design models are often just extensions of the requirements models.

What is O-O program: An object-oriented program consists of a set of program objects that cooperate to accomplish a result. Each program object has program logic and any necessary attributes encapsulated into a single unit. These objects work together by sending each other messages and working in concert to support the functions of the main program.

Identify classes?

O-O program The previous slide shows how an object-oriented program works. Hidden, it also illustrates the three-layer architecture: Abstract Three Layer Architecture

Objective of O-O design: The objective of object-oriented design is to identify and specify all the objects that must work together to carry out each use case. As shown in Figure 10-1, these objects include user-interface objects, problem domain objects, and data access objects. Can you identify these objects?

The OO diagrams: O-O analysis: O-O design: Use case, Use case description, Activity diagram, Domain Model Diagrams, System Sequence Diagram, State Machine Diagram O-O design: Component diagrams, deployment diagrams, design class diagrams, interaction diagrams, state machine diagrams, and package diagrams.

Objective: A major responsibility of detailed design is to identify and describe each set of objects within each layer and to identify and describe the interactions or messages that are sent between these objects. The most important model in object-oriented design is a sequence diagram The other major design model is the design class diagram

Revision: An object class (or a class) is… Set of people Places Things Or transactions that share common attributes and perform common functions to help an organization reaches its goals.

Examples: People: employees, vendors, customers Places: warehouses, office, branches, shipping docks Things: products, office equipment, supplies Transaction: purchases, sales, returns, payments

From the narrative? People: dog-owner, vet, person Places: pet shop, clinic Things: Ball and……..dog Transaction: payment, treatment OO: a class is an abstraction or model of a real concept.

Domain Classes with MS Visio:

Object Instances:

Attributes:

Design Class Diagrams (DCD):

Messages:

Example: Draw money from ATM Processes: Insert credit card Enter PIN Enter Amount What happens behind UI? Verification from bank system ……

Classes? Customer ATM: ATM System Bank System

Interaction: What message/communication takes place between customer and ATM? Customer wants to enter PIN If verified, Customer wants to draw money

Three layer Architecture: user-interface objects, problem domain objects, and data access objects.

Two Things: Identifying design classes: use interactions to add operations to classes. Identifying stereotypes in UML models

Questions: Identify the classes Draw the SD Sort-out the interactions or messages Add the operations/behaviour Add the ‘three layer diagram’