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What is Analysis and Designthe problem and requirements rather than how a solution is defined solution that system fulfils the requirements rather than its implementation Hoa Sen Uni

Object-Oriented Analysis and

Design

with Patterns, Process, and the UML

Introduction

 Welcome!

 Introduction

– Course leader: Dr Trần Vũ Bình– Participants:

 Prerequisites: Object-Oriented Programming

 Logistics

Overview and Objectives

 Learn how to “think in objects”

 Requirements and analysis of the problem domain

Team Project – Online Enrolment

 Your client:

– Hoa Sen University

 Your goal:

– Design a system to allow users to select

appropriate course, arrange schedule as

available

curriculum.

Project Task

 Assignment 1

– Prepare requirement document

– Write use cases

– Develop Domain Model

 Assignment 2

– Write Design Document

– Implement the system (desktop version)

– System Demo

What is OOAD?

Lecture 1

Today’s lecture topic

 Object oriented concepts revisited

 What’s OOAD?

 Functional decomposition and its problem

 What’s UML?

 Software Development Process

What is Analysis and Design

the problem and requirements rather

than how a solution is defined

solution that system fulfils the

requirements rather than its

implementation

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What is O-O A&D?

 The essence of O-O A&D is to consider a

problem domain and logical solution from

the perspective of objects (things,

concepts, or entities)

describing the objects – or concepts- in

the problem domain

software objects (things, concepts, or

entities) that have attributes and methods

Object vs Function Oriented Analysis

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Library Information System

Functional Decomposition

 A very simple development case

– You are asked to write code to access a list of shapes that were stored in a database then

display them

 What steps we need to achieve this?

1.Locate the list of shapes in the database

2.Open up the list of shapes

3.Sort the list according to some order

4.Display the individual shapes on the monitor

Functional Decomposition

 We might breakdown some step further

– Identify the type of shapes

– Get the location of the shape

– Call the appropriate function that will display

the shape, giving it the shape’s location

 This is called functional decomposition

because the analyst breaks down

(decomposes) the problem into the

functional steps that compose it.

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How do people do things

 Case:

– You are an instructor at a seminar People in

your seminar have another class to attend

following yours, but don’t know where it is

located One of your responsibilities is to

make sure everyone knows how to get to the

next class.

A “software like” option

– Get list of people in the class

– For each person on this list,

do the following:

 Find the next class he or she

is taking

 Find the location of that class

 Find the way to get from your

classroom to the persona’s

next class

 Tell the person how to get to

his or her next class

– A program that gives someone directions from your classroom to any other classroom

– A control program that works for each person in the class and does the required steps for each person

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A “human like” option

 What’s the alternatives?

– Post a directions to go from this classroom to

the other classrooms and tell everyone in the

class

“ I have posted the locations of the other classes following this in the back of the room, as well as the locations of the other classrooms Please use them to go to your next classroom ”

– Assume everyone knows what his or her next

class is

 Option 1: giving explicit directions to

everyone – pay attention to lots of details

You are responsible for everything

 Option 2: giving general instructions and then expect each person will figure out how to do

the task individually

– Two kinds of objects

 Instructor: responsible for posting the instruction

 Students: knowing their own next classes, able to follow the instruction

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Dealing with changing

requirements

 Impact

– What if you need to distinguish postgraduate

students from undergraduate students?

– Option 1: change the control program a lot

– Option 2: add an additional routine for

graduate students to follow

 The second case can minimize changes

Dealing with changing

requirements

 What makes it happen?

– The people are responsible for their own

behaviour

– The control program can talk to different types

of people as if they were exactly the same

– The control program does not need to know

about any special steps that students might

need to take when moving from class to class

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Key Steps in OOAD [1]

 Use Case: a textual description or “story”

describing the system

 Play a Dice Game: Player requests to roll

the dice System presents results: If the

dice face value totals seven, player wins;

otherwise, player loses.

Key steps in OOAD [2]

 a domain model that shows the noteworthy

domain concepts or objects, attributes, and

associations

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Player name

DiceGame

Die faceValue Rolls

Key steps in OOAD [3]

 Interaction Diagram: shows the flow of messages

between software objects (method invocation)

:DiceGame play()

Key steps in OOAD [4]

 Class Model: shows attributes, methods and

associations for software (solution) objects (not

domain objects!)

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2

Die faceValue : int

getFaceValue() : int roll()

Iterative and Evolutionary

Development

 Iterative development

– Development is organized into a series of

short, fixed-length mini-projects called

iterations.

– the outcome of each is a tested, integrated,

and executable partial system.

– Known as iterative and incremental

development

Iterative and evolutionary

Test & Integration

& More Design

Final Integration

& System Test

Requirements Design

3 weeks (for example)

The system grows incrementally.

Feedback from iteration N leads to refinement and adaptation of the requirements and design in iteration N+1.

Iterations are fixed in

length, or timeboxed.

Time

Implementation &

Test & Integration

& More Design Final Integration

& System Test

Handle change on iterative project

Early iterations are farther from the "true

path" of the system Via feedback and

adaptation, the system converges towards

the most appropriate requirements and

design

In late iterations, a significant change in requirements is rare, but can occur Such late changes may give an organization a competitive business advantage

one iteration of design, implement, integrate, and test

How long should an iteration be?

 Most iterative methods recommend an

iteration length between two and six weeks.

 Iteration are timeboxed, or fixed in length

 Date slippage is illegal

 If it seems difficult to meet the deadline, the

recommended response is to de-scope –

remove tasks or requirements from the

iteration, and include them in a future

iteration

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How to do Iterative and Evolutionary

Analysis and Design?

Iteration 1 Iteration 2 Iteration 3 Iteration 4 Iteration 5

design, UML

start coding &

testing

a 3-week iteration

de-scope iteration goals if too much

final check -in and code- freeze for the iteration

demo and 2-day requirements workshop

next iteration planning meeting;

Agile Methods and attitudes

 Agile development methods usually apply

timeboxed iterative and evolutionary

development, employ adaptive planning,

promote incremental delivery and include

other values and practices that encourage

agility – rapid, and flexible response to

Agile Modelling

 Adopting an agile method does not mean

avoiding any modelling

 The purpose of modelling and models is

primarily to support understanding and

communication, not documentation

 Don’t model or apply the UML to all or

most of the software design

 Use the simplest tool possible

Agile modelling (cont)

 Don’t model alone

 Create models in parallel

 Use “good enough” simple notation while

sketching with a pen on paper

 Developers themselves should do the OO

design modelling, for themselves, not to

create diagrams that are given to other

programmers to implement.

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Layers and textbook case study

primary focus

of case studies explore how to design objects

secondary focus

Case study strategy

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Introduces just those

analysis and design skills

related to iteration one

Additional analysis and design skills introduced

 Case one: The NextGen POS

system

– A POS system is a computerized

application used (in part) to record

sales and handle payments

– Hardware: computer, bar code

scanner

– Software

– Interfaces to service applications:

tax calculator, inventory control

 Case Two: The Monopoly Game

System