OBJECT-ORIENTED ANALYSIS AND DESIGN (1)

Sucha Smanchatsucha.smanchat@acm.org

UML in System Analysis and Design Steps in OOAD using UML

Use Case Diagram Sequence Diagram / Communication Diagram Class Diagram State Machine Diagram Activity Diagram Package Diagram Component Diagram Deployment Diagram

A Note UML is somewhat hard

One problem can be solved by different designs

No exact answer UML Specification is continuously updated

And it’s !@#$% hard to catch up Different books say things differently The steps in this presentation is but one

common guideline

Step 1:Use Case Diagram Identify functional requirements of

existing and/or new system Identify stakeholders/users of the

system Draw system boundary Draw each functional requirement as a

use case Less or more use cases? Why?

Represent users as actors

Step 1:Use Case Diagram(cont.) Use the <<extend>> and <<include>>

relationships as needed Usually, an extending use case is adding extra

function to the extended use case Usually, an included use case is a common

function which is shared by many other use cases Write use case description for each and

every use case Format varies - see

http://en.wikipedia.org/wiki/Use_case

Use Case Description ExampleName:Primary Actor:Stakeholders and Interests:Preconditions: Postconditions:Main Scenario:1.2.…Extensions:1a.2a.

Adapted fromCraig Larman, “Applying UML and Patterns: An Introduction to Object- Oriented Analysis and Design and the Unified Process”, 2nd Ed., Prentice Hall, 2002.

Exercise Draw a ‘complete’ use case diagram

(including use case description) for one of the following scenarios (at least 3 use cases) Automatic Teller Machine (ATM) An online game server A customer support system for a product of

your choice Or a system being used in your work

Step 2:Sequence Diagram Based on the use case diagram, draw a

sequence diagram (or communication/collaboration diagram) for each use case

There might be more than one sequence diagram to represent alternate routes

When drawing sequence diagram, think of the real world scenario (that you write in use case description) and select potential objects/classes

Step 2:Sequence Diagram (Cont) Drawing sequence diagram helps identify

classes and objects in the system along with the communications between them

The communications, in turn, identify the behavior of the classes and objects in the system

How do you tell what should be a class/object? If it’s not a class, what should it be?

Step 2:Sequence Diagram (Cont) Distinguish different types of

communications (refer to UML slides) Use them appropriately Be careful about notation Do you need to refer to a specific object

of a class?

Exercise Draw sequence diagrams for the use

cases in your use case diagrams Try to be as much detailed as possible

Step 3:Class Diagram Most of the objects/classes in the system

are identified in sequence diagram Additional classes may (likely) be required

Draw classes identified from step 2 Add necessary attributes Specify data type of the attributes Specify visibility of the attributes

Usually ‘private’ (encapsulation / data hiding) ‘public’ or ‘protected’ may be used (e.g. static

variable)

Step 3:Class Diagram (cont) Add behavior (methods) as identified by

communications between objects in sequence diagrams

What can an object do? What should an object do for other objects? Specify method’s parameters

Parameter VS Argument? Specify visibility

Usually ‘public’ or ‘protected’, but ‘private’ is possible for method used within the class

Step 3:Class Diagram (cont) Add relationships between classes

Association (uni-directional / bi-directional) Generalization (inheritance) Aggregation Composition

Specify name of relationship and/or roles of the classes involved

Specify multiplicity (0..1, 1..1, 0..m, 1..m)

Step 3:Class Diagram (cont) It is possible to specify the type of classes by

inscribing <<stereotype>> with class name GUI classes may be inscribed with <<boundary>> Controller classes (classes that contain business

rules and/or calculations) may be inscribed with <<controller>>

Classes that model data (database) may be inscribed with <<entity>>

Be careful as stereotype may cause confusion Do not use <<interface>> for GUI classes

Exercise Draw a class diagram for your system

using the objects/classes and their behavior obtained from the sequence diagrams Again, try to be as much detailed as

possible

SummaryFirst Half Software Development Methodology SDLC ? ERD & DFD Object-Oriented Concept & UML OOAD

Use Case Diagram Sequence Diagram Class Diagram