Course introduction
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Using UML, Patterns, and Java
Object-Oriented Software Engineering
Chapter 1: Introduction
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Requirements for this Class
i
You are proficient in a programming language, but you have no
experience in analysis or design of a system
i
You want to learn more about the technical aspects of analysis
and design of complex software systems
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Objectives of the Class
i
Appreciate Software Engineering:
Build complex software systems in the context of frequent change
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Understand how to
produce a high quality software system within time
while dealing with complexity and change
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Acquire technical knowledge (main emphasis)
Acquire managerial knowledge
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Acquire Technical Knowledge
i
i
i
Understand System Modeling
Learn UML (Unified Modeling Language)
Learn different modeling methods:
i
Use Case modeling
Object Modeling
Dynamic Modeling
Issue Modeling
Learn how to use Tools:
CASE (Computer Aided Software Engineering)
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Tool: Rose or HiMEMv.10
Component-Based Software Engineering
Learn how to use Design Patterns and Frameworks
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Acquire Managerial Knowledge
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Understand the Software Lifecycle
Process vs Product
Learn about different software lifecycles
Greenfield Engineering, Interface Engineering, Reengineering
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Readings
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Required:
Bernd Bruegge, Allen Dutoit: “Object-Oriented Software
Engineering: Using UML, Patterns, and Java”, Prentice Hall, 2003.
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Recommended:
Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides:
“Design Patterns”, Addison-Wesley, 1996.
Grady Booch, James Rumbaugh, Ivar Jacobson, “The Unified
Modeling Language User Guide”, Addison Wesley, 1999.
K. Popper, “Objective Knowledge, an Evolutionary Approach,
Oxford Press, 1979.
i
Additional books may be recommended during individuals
lectures
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Outline of Today’s Lecture
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High quality software: State of the art
Modeling complex systems
Functional vs. object-oriented decomposition
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Dealing with change:
Software lifecycle modeling
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Reuse:
Design Patterns
Frameworks
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Concluding remarks
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Can you develop this?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Limitations of Non-engineered Software
Requirements
Software
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
11
The Current Big Problem
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Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
12
One Possible Answer
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Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
13
Software Development Methods
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Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
14
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Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Why Modeling? Consider the problem of Scale……….
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Bernd Bruegge & Allen H. Dutoit
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Object-Oriented Software Engineering: Using UML, Patterns, and Java
16
Influence of System Stakeholders
Persons who have an interest in the construction of a software system and
might include
customers
users
developers
project mangers
marketers
maintainers
- Different concerns to guarantee and/or optimize
i
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Stakeholders’ Concerns
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18
Users
i
People who use the system.
End users are concerned primarily with a
system’s ease of use.
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Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Users - 2
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End User are often the domain experts.
- consider a aircraft pilot, automobile
driver, homemaker
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Customers
i
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People who pay for the system’s development.
Customer are not always users.
Customer’s concerns include the system’s
- cost, functionality, lifetime,
- development time/time to market
- quality, flexibility to do many things on
delivery day, and over its lifetime
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Manager
i
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Management stakeholders include those
managers from the development organization/customer
organization
Manager’s concerns include
Pay back development costs
Maintaining the workforce’s core competency
and organization training
Investing to achieve strategic goals
Keeping development costs as low as possible
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Manager -2
Adhering to the development schedule
Maintaining product quality
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Other Stakeholders
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Developers are concerned about languages, technology, and the
best to solve the problem
Maintainers are a system they can fix, improve, modify, extend,
and so forth.
Administrators want a system they can tune, configure, deploy,
and so forth.
Marketers want feature that meet or exceed the competitive
price.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Software engineering concepts
Project
*
Activity
is produced by
WorkProduct
*
consumes
*
Task
System
*
Participant
Model
Time
Document
Bernd Bruegge & Allen H. Dutoit
Resources
Equipment
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Project: purpose is to develop a software system
consists of a number of Activities.
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Activity: consists of a number of tasks.
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Task: consumes Resources and produces a WorkProduct.
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WorkProduct: can be either a System, a Model, or a Document.
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Resource: are either Participant, Time, Equiment.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Participant
- client: orders and pay for the system
- developer: constructs the system
- project manger: plans and budgets the project and
coordinates the developers and client.
- end-users: are supported by the system
All the above persons involves in the project as participants.
Responsibilities in the project or the system as role.
A role is assigned with a set of tasks and is assigned to a
participant.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Examples of roles in
software engineering
for TicketDistibuter Project
Role
Responsibilities
Client
Train company
User
Travelers
Manager
boss
Developer
Analyst, programmer, tester
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Software Production has a Poor Track Record
Example: Space Shuttle Software
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Cost: $10 Billion, millions of dollars more than planned
Time: 3 years late
Quality: First launch of Columbia was cancelled because of a
synchronization problem with the Shuttle's 5 onboard
computers.
Error was traced back to a change made 2 years earlier when a
programmer changed a delay factor in an interrupt handler from
50 to 80 milliseconds.
The likelihood of the error was small enough, that the error caused
no harm during thousands of hours of testing.
i
Substantial errors still exist.
Astronauts are supplied with a book of known software problems
"Program Notes and Waivers".
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Quality of today’s software….
i
The average software product released on the market is not
error free.
QuickTime?and a
Cinepak decompressor
are needed to see this picture.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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…has major impact on Users
QuickTime?and a
decompressor
are needed to see this picture.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Software Engineering: A Problem Solving Activity
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Analysis: Understand the nature of the problem and break the
problem into pieces
Synthesis: Put the pieces together into a large structure
For problem solving we use
i Techniques (methods):
Formal procedures for producing results using some well-defined
notation
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Methodologies:
Collection of techniques applied across software development and
unified by a philosophical approach
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Tools:
Instrument or automated systems to accomplish a technique
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Software Engineering: Definition
Software Engineering is a collection of techniques,
methodologies and tools that help
with the production of
i
i
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a high quality software system
with a given budget
before a given deadline
while change occurs.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Scientist vs Engineer
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Computer Scientist
Proves theorems about algorithms, designs languages, defines
knowledge representation schemes
Has infinite time…
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Engineer
Develops a solution for an application-specific problem for a client
Uses computers & languages, tools, techniques and methods
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Software Engineer
Works in multiple application domains
Has only 3 months...
…while changes occurs in requirements and available technology
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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20
Factors affecting the quality of a software system
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Complexity:
The system is so complex that no single programmer can understand it
anymore
The introduction of one bug fix causes another bug
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Change:
The “Entropy” of a software system increases with each change: Each
implemented change erodes the structure of the system which makes the
next change even more expensive (“Second Law of Software
Dynamics”).
As time goes on, the cost to implement a change will be too high, and
the system will then be unable to support its intended task. This is true
of all systems, independent of their application domain or technological
base.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Why are software systems so complex?
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The problem domain is difficult
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The development process is very difficult to manage
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Software offers extreme flexibility
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Software is a discrete system
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Dealing with Complexity
1.
2.
3.
Abstraction
Decomposition
Hierarchy
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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What is this?
B-27
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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What is this?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
B-28
39
What is this?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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1. Abstraction
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Inherent human limitation to deal with complexity
The 7 +- 2 phenomena
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Chunking: Group collection of objects
Ignore unessential details: => Models
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Models are used to provide abstractions
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System Model:
Object Model: What is the structure of the system? What are the
objects and how are they related?
Functional model: What are the functions of the system? How is
data flowing through the system?
Dynamic model: How does the system react to external events? How
is the event flow in the system ?
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Task Model:
PERT Chart: What are the dependencies between the tasks?
Schedule: How can this be done within the time limit?
Org Chart: What are the roles in the project or organization?
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Issues Model:
What are the open and closed issues? What constraints were posed
by the client? What resolutions were made?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Interdependencies of the Models
System Model (Structure,
Functionality,
Dynamic Behavior)
Issue Model
(Proposals,
Arguments,
Resolutions)
Task Model
(Organization,
Activities
Schedule)
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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The “Bermuda Triangle” of Modeling
System Models
Object Model
Forward
Engineering
Functional
Model
Constraints
Arguments
Issues
Pro Con
Proposals
Issue Model
Bernd Bruegge & Allen H. Dutoit
class...
class...
class...
Code
Reverse
Engineering
Dynamic Model
Org Chart
PERT Chart
Gantt Chart
Task Models
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Model-based software Engineering:
Code is a derivation of object model
Problem Statement : A stock exchange lists many companies.
Each company is identified by a ticker symbol
Analysis phase results in cbject model (UML Class Diagram):
*
StockExchange
*
Lists
Company
tickerSymbol
Implementation phase results in code
public class StockExchange
{
public Vector m_Company = new Vector();
};
public class Company
{
public int m_tickerSymbol
public Vector m_StockExchange = new Vector();
};
AAgood
goodsoftware
softwareengineer
engineerwrites
writesas
aslittle
littlecode
codeas
aspossible
possible
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Example of an Issue: Galileo vs the Church
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What is the center of the Universe?
Church: The earth is the center of the universe. Why? Aristotle says
so.
Galileo: The sun is the center of the universe. Why? Copernicus
says so. Also, the Jupiter’s moons rotate round Jupiter, not around
Earth.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Issue-Modeling
Issue:
What is the
Center of the
Universe?
Resolution (1998):
The church declares
proposal 1 was wrong
Resolution (1615):
The church
decides proposal 1
is right
Proposal2:
The sun!
Proposal1:
The earth!
Pro:
Pro:
Con:
Jupiter’s moons rotate
around Jupiter, not
around Earth.
Aristotle
says so.
Pro:
Copernicus
says so.
Change will disturb
the people.
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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2. Decomposition
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A technique used to master complexity (“divide and conquer”)
Functional decomposition
The system is decomposed into modules
Each module is a major processing step (function) in the application
domain
Modules can be decomposed into smaller modules
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Object-oriented decomposition
The system is decomposed into classes (“objects”)
Each class is a major abstraction in the application domain
Classes can be decomposed into smaller classes
Which decomposition is the right one?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Functional Decomposition
System
Function
Read Input
Read Input
Transform
Transform
Produce
Output
Level 1 functions
Level 2 functions
Produce
Output
Add R1, R10
Load R10
Bernd Bruegge & Allen H. Dutoit
Top Level functions
Object-Oriented Software Engineering: Using UML, Patterns, and Java
Machine Instructions
49
Functional Decomposition
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Functionality is spread all over the system
Maintainer must understand the whole system to make a single
change to the system
Consequence:
Codes are hard to understand
Code that is complex and impossible to maintain
User interface is often awkward and non-intuitive
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Example: Microsoft Powerpoint’s Autoshapes
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Functional Decomposition: Autoshape
Autoshape
Mouse
click
Change
Rectangle
Draw
Change
Change
Oval
Change
Circle
Draw
Rectangle
Bernd Bruegge & Allen H. Dutoit
Draw
Oval
Draw
Circle
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Object-Oriented Software Engineering: Using UML, Patterns, and Java
52
What is This?
Bernd Bruegge & Allen H. Dutoit
Model of an Eskimo
Eskimo
Size
Dress()
Smile()
Sleep()
*
Shoe
Size
Color
Type
Wear()
Bernd Bruegge & Allen H. Dutoit
Coat
Size
Color
Type
Wear()
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Iterative Modeling then leads to ....
lives in
Cave
Lighting
Enter()
Leave()
Eskimo
Size
Dress()
Smile()
Sleep()
moves
around
Outside
Temperature
Light
Season
Hunt()
Organize()
*
Entrance
Windhole
Diameter
MainEntrance
Size
but is it the right model?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Alternative Model: The Head of an Indian
Indian
Hair
Dress()
Smile()
Sleep()
Ear
Size
listen()
*
Bernd Bruegge & Allen H. Dutoit
Face
Nose
smile()
close_eye()
Mouth
NrOfTeeths
Size
open()
speak()
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Class Identification
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Class identification is crucial to object-oriented modeling
Basic assumption:
1. We can find the classes for a new software system: We call this
Greenfield Engineering
2. We can identify the classes in an existing system: We call this
Reengineering
3. We can create a class-based interface to any system: We call this
Interface Engineering
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Why can we do this? Philosophy, science, experimental
evidence
What are the limitations? Depending on the purpose of the
system different objects might be found
How can we identify the purpose of a system?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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What is this Thing?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Modeling a Briefcase
BriefCase
Capacity: Integer
Weight: Integer
Open()
Close()
Carry()
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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A new Use for a Briefcase
BriefCase
Capacity: Integer
Weight: Integer
Open()
Close()
Carry()
SitOnIt()
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Questions
i
Why did we model the thing as “Briefcase”?
Why did we not model it as a chair?
i What do we do if the SitOnIt() operation is the most
frequently used operation?
i The briefcase is only used for sitting on it. It is never
opened nor closed.
i
Is it a “Chair”or a “Briefcase”?
i
How long shall we live with our modeling mistake?
Bernd Bruegge & Allen H. Dutoit
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3. Hierarchy
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We got abstractions and decomposition
This leads us to chunks (classes, objects) which we view with object
model
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Another way to deal with complexity is to provide simple
relationships between the chunks
One of the most important relationships is hierarchy
2 important hierarchies
"Part of" hierarchy
"Is-kind-of" hierarchy
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Part of Hierarchy
Computer
I/O Devices
CPU
Memory
Cache
ALU
Program
Counter
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Is-Kind-of Hierarchy (Taxonomy)
Cell
Muscle Cell
Striate
Smooth
Bernd Bruegge & Allen H. Dutoit
Blood Cell
Red
White
Nerve Cell
Cortical
Pyramidal
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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So where are we right now?
i
Three ways to deal with complexity:
Abstraction
Decomposition
Hierarchy
i
Object-oriented decomposition is a good methodology
Unfortunately, depending on the purpose of the system, different
objects can be found
i
How can we do it right?
Many different possibilities
Our current approach: Start with a description of the functionality
(Use case model), then proceed to the object model
This leads us to the software lifecycle
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
64
Software Lifecycle Activities
Requirements
Elicitation
Analysis
Expressed in
Terms Of
System
Design
Structured By
...and their models
Object
Design
Implementation
Implemented
By
Realized By
Verified
By
class...
class...
class...
Use Case
Model
Application
Subsystems
Domain
Objects
Bernd Bruegge & Allen H. Dutoit
Testing
Solution
Domain
Objects
Source
Code
Object-Oriented Software Engineering: Using UML, Patterns, and Java
?
class.... ?
Test
Cases
65
Software Lifecycle Definition
i
Software lifecycle:
Set of activities and their relationships to each other to support the
development of a software system
i
Typical Lifecycle questions:
Which activities should I select for the software project?
What are the dependencies between activities?
How should I schedule the activities?
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
66
Reusability
i
i
A good software design solves a specific problem but is general
enough to address future problems (for example, changing
requirements)
Experts do not solve every problem from first principles
They reuse solutions that have worked for them in the past
i
Goal for the software engineer:
Design the software to be reusable across application domains and
designs
i
How?
Use design patterns and frameworks whenever possible
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
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Design Patterns and Frameworks
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Design Pattern:
A small set of classes that provide a template solution to a recurring
design problem
Reusable design knowledge on a higher level than datastructures
(link lists, binary trees, etc)
i
Framework:
A moderately large set of classes that collaborate to carry out a set
of responsibilities in an application domain.
i
i
Examples: User Interface Builder
Provide architectural guidance during the design phase
Provide a foundation for software components industry
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Patterns are used by many people
i
Chess Master:
i
Software Engineer
Openings
Middle games
End games
i
Writer
Tragically Flawed Hero
(Macbeth, Hamlet)
Romantic Novel
User Manual
i
Composite Pattern: A collection
of objects needs to be treated
like a single object
Adapter Pattern (Wrapper):
Interface to an existing system
Bridge Pattern: Interface to an
existing system, but allow it to
be extensible
Architect
Office Building
Commercial Building
Private Home
Bernd Bruegge & Allen H. Dutoit
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69
Summary
i
Software engineering is a problem solving activity
Developing quality software for a complex problem within a limited
time while things are changing
i
There are many ways to deal with complexity
i
Modeling, decomposition, abstraction, hierarchy
Issue models: Show the negotiation aspects
System models: Show the technical aspects
Task models: Show the project management aspects
Use Patterns: Reduce complexity even further
Many ways to do deal with change
Tailor the software lifecycle to deal with changing project
conditions
Use a nonlinear software lifecycle to deal with changing
requirements or changing technology
Provide configuration management to deal with changing entities
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