Lecturer: Dr. AJ Bieszczad Chapter 66-1 Object-Oriented analysis and design Special nature of OO development Use cases Design with UML OO system design.

Lecturer: Dr. AJ Bieszczad

Chapter 6 6-1

Object-Oriented analysis and design

• Special nature of OO development

• Use cases

• Design with UML

• OO system design

• OO program design

• OO measurements


Chapter 6 6-2

Object orientation

• identity

• abstraction

• classification

• encapsulation

• inheritance

• polymorphism

• persistence


Chapter 6 6-3

Objects and classes

• Every object has a name (also called a reference or handle).

• Objects can have attributes (such as color, size, location).

• Objects can have operations or behaviors (such as takeoff, land, repair).

• Each object is an instance of a class.• A specific implementation of an operation for a

certain class is called a method.


Chapter 6 6-4

Classification


Chapter 6 6-5

Forming a hierarchy


Chapter 6 6-6

Table 6.1: Tendency for change when using OO paradigm (Jacobson et al. 1995)

Characteristic of software product/project Probability for change

Objects derived from the application lowLong-lived information structures lowPassive object’s attribute mediumSequences of behavior mediumInterface with the outside world highFunctionality high


Chapter 6 6-7

OO design• Usually uses an OO requirements representation• System design identifies and represents objects and classes,

plus details of each objects attributes and behaviors.• System design also identifies interactions and relationships.• Program design inserts computational features in the

models.• Program design inserts class library details.• Program design considers nonfunctional requirements to

enhance design.


Chapter 6 6-8

OO and testing


Chapter 6 6-9

Use cases

• Diagrams have four elements:– actors– cases– extensions– uses


Chapter 6 6-10

Identifying participants• What users or groups use the system to perform a task?• What users or groups are needed so that the system can

perform its functions?• What external systems use the system to perform a task?• What external systems, users or groups send

information to the system?• What external systems, users or groups receive

information from the system?


Chapter 6 6-11

Example: Service station


Chapter 6 6-12

Service station use case diagram 1


Chapter 6 6-13



Chapter 6 6-14



Chapter 6 6-15

UML and the OO process

• Workflow diagrams

• Object model

• Sequence diagrams

• Collaboration diagrams

• Package diagrams

• Component diagrams

• Deployment diagrams


Chapter 6 6-16

UML support for development process


Chapter 6 6-17

First cut at object classes

• Structures• External systems• Devices• Roles• Operating procedures• Places• Organizations• Things that are manipulated by the system to be built


Chapter 6 6-18

Class box example


Chapter 6 6-19

Inheritance relationship


Chapter 6 6-20

Association relationship


Chapter 6 6-21

Types of class relationships


Chapter 6 6-22

UML notes and qualifies


Chapter 6 6-23

Service Station – first take


Chapter 6 6-24

Service Station – second take


Chapter 6 6-25

Service Station – final cut


Chapter 6 6-26

Class name: refuelCategory: serviceExternal documents:Export control: PublicCardinality: nHierarchy:

Superclasses: servicesAssociations:

fuel in association <name>Operation name: price

Public member of: refuelDocumentation:

// Calculates fuel final pricePreconditions:

gallons > 0Object diagram: (unspecified)

Semantics:final_price = gallons * priceObject diagram: (unspecified)

Concurrency: sequential

Public interface:Operations:

pricePrivate interface:

Attributes:gallonsprice

Implementation:Attributes:

gallonsprice

State machine: noConcurrency: sequentialPersistence: transient


Chapter 6 6-27

Service Station – package diagram


Chapter 6 6-28

Sequence Station – sequence diagram for the refuel use case


Chapter 6 6-29

Service Station – collaboration diagram for the perking use case


Chapter 6 6-30

State diagram example


Chapter 6 6-31

State diagram for Fuel class


Chapter 6 6-32

State diagram for Part class


Chapter 6 6-33

State diagram for Inventory class


Chapter 6 6-34

Activity diagram


Chapter 6 6-35

Activity diagram for Inventory class


Chapter 6 6-36

Guidelines for building classes

• What needs to be “processed” in some way?

• What items have multiple attributes?

• When do you have more than one object in a class?

• What is based on the requirements themselves, not derived from your understanding of the requirements?

• What attributes and operations are always applicable to a class or object?


Chapter 6 6-37

Guidelines for identifying behaviors

• Imperative verbs

• Passive verbs

• Actions

• Things or reminded events

• Roles

• Operating procedures

• Services provided by an organization


Chapter 6 6-38

Program design considerations

• Nonfunctional requirements

• Reused components

• Reusable components

• User interface requirements

• Data structure and management details


Chapter 6 6-39

Transition from paper to screen


Chapter 6 6-40

Possible design for new billing screen


Chapter 6 6-41

Implementing classes using relational database


Chapter 6 6-42

Observer pattern - relationships


Chapter 6 6-43

Observer pattern – sequence diagram


Chapter 6 6-44

Table 6.5: Lorenz and Kidd metrics collection in different phases of development.

Phase

Metric

RequirementsDescription

System Design Program Design Coding Testing

Number of scenarioscripts

X

Number of key classes X XNumber of support classes XAverage number ofsupport classes per keyclass

X

Number of subsystems X XClass size X X XNumber of operationsoverridden by a subclass

X X X X

Number of operationsadded by a subclass

X X X

Specialization index X X X X


Chapter 6 6-45

Table 6.7: Where to capture OO metrics.

Phase

Metric

Use cases Classdiagrams

Inter-actiondiagrams

Class descrip-tions

Statediagrams

Packagediagrams

Number of scenario scripts XNumber of key classes XNumber of support classes XAverage number ofsupport classes per keyclass

X

Number of subsystems XClass size X XNumber of operationsoverridden by a subclass

X

Number of operationsadded by a subclass

X

Specialization index XWeighted methods in class XDepth of inheritance XNumber of children XCoupling between objects XResponse for a class XLack of cohesion inmethods

X

Average operation size XAverage number ofparameters per operation

X

Operation complexity XPercent public andprotected

X

Public access to datamembers

X

Number of root classes XFan-in/fan-out X


Chapter 6 6-46

Object-oriented view of the Service Station


Chapter 6 6-47

Class hierarchy for the Service Station


Chapter 6 6-48

Table 6.6: Chidamber and Kemerer metrics collection in different phases of development.

Phase

Metric

System Design Program Design Coding Testing

Weighted methods perclass

X X X

Depth of inheritance X X XNumber of children X X XCoupling between objects X XResponse for a class X XLack of cohesion ofmethods

X X X


Chapter 6 6-49

Measuring Service Station system design


Chapter 6 6-50

Measuring Service Station program design


Chapter 6 6-51

Measuring from a sequence diagram

Lecturer: Dr. AJ Bieszczad Chapter 66-1 Object-Oriented analysis and design Special nature of OO development Use cases Design with UML OO system design.

Documents

aj bieszczad chapter

classification slide

testing slide

hierarchy slide

oo design

development process

use cases diagrams

service station