Object-Oriented Analysis
and Design Methods
Lecture Objectives
To understand the process of identifying
and creating objects for a system
To describe a method for developing
objects for an object-oriented system
To describe the representations that can be
used for objects and their relationships
To discuss the dynamic aspects of
Too Many Methodologies!
Booch Object-Oriented Design
Rumbaugh Object Modeling Technique
Shlaer and Mellor Analysis and Design
Jacobson Objectory
Wirfs-Brock Responsibility Driven Design
Martin and Odell Object-Oriented Analysis
and Design
Object-Oriented Analysis
Identify the objects and classes Identify the object attributes
Identify operations on objects and classes Define object and class relationships
Identify the objects and
classes
Grammatical Analysis
Nouns are objects and attributes
Verbs are operations or services
Tangible entities (things), roles, events,
interactions, etc. in application domain
Use behavioural approach
Participants in behaviours as objects
Identify the object
attributes
Specify attributes (instance variables) of
objects in problem domain
These are to be recorded, displayed,
Identify operations on
objects and classes
Operations that are used to interact with
the objects and classes
Each class has a protocol that captures the
messages or operations that could be handled by the class or its instances
Users or “clients” of classes and objects
Example Scenario
“The Office Information Retrieval System
(OIRS) can file documents under some name
in one or more indexes, retrieve documents,
display and maintain document indexes,
archive documents and destroy documents.
The system is activated by a request from the
user and always returns a message to the user
Define object and class
relationships
Capture relationship between classes. Typical relationships:
Inheritance
Organisation of classes or entity types in
problem domain
One-to-One, One-to-Many, Many-to-Many
relationships that exist between objects that
Example of Inheritance
Person
Student Employee
Example of Other
Relationships
Country City
Person Company
File User
Has-capital
Works-for
Accessible-by One-to-One
One-to-Many
Model dynamic concepts
State transition diagrams
Specify states of the objects
Specify events that trigger transitions
Specify actions taken due to transitions
Data flow diagrams
Describe flow of objects and information
Timing diagrams
Data flow diagram
Customer
Update Verify
Account password
amount
cash
Coded password
old balance Password
ok
Timing diagrams
Caller Phone line Callee
Caller lifts receiver
Dial tone begins Dials number
Ringing tone Phone rings
Answers phone
Tone stops Ringing stops
Phones connected Phones connected
Unified Modeling Language Approach OOA
User view model – system represented
from the user’s perspective by developing use-case model
Structural view model – data and function
is view from inside the system, static
Use Case
Scenario based technique for requirement
elicitation
Use case should achieve the following
objectives :
Define functional and operational
requirements of the system
Provide clear description of how end user and
the system will interact with one another
Use Case Diagram Elements
Actor : Entities that interact with
the system
Person, machine, another
system etc
Represent roles that a user
play in the system
Use case
Sequence of transaction
performed by the system
Initiated by an actor to
invoke certain function in the system
Sensor
Customer Credit System
Use Case Diagram For The Library
Borrow copy of book Reserve book
Extend loan Return copy
of book BookBorrower
Return copy of book
Update catalog
Librarian Browse
Identify Objects and Classes
Object
Thing that can interact with
Reacts when send messages
concept, abstraction or
thing that has sharp
boundaries and meaning for an application
Object has
State : value of property at
a given time
Behavior : objects action
and reaction
Identity : distinguishes from
other objects Object
Thing that can interact with Reacts when send
messages
concept, abstraction or
thing that has sharp
boundaries and meaning for an application
Object has
State : value of property at
a given time
Behavior : objects action
and reaction
Identity : distinguishes from
Class
A sets of objects with an
equivalent roles in the system
Every object belongs to a
class
Example :
Tangible : book, copy,
course
Roles : library member,
student
Events : arrival, leaving,
request
Interaction : meeting,
intersection Class
A sets of objects with an
equivalent roles in the system
Every object belongs to a
class
Example :
Tangible : book, copy,
course
Roles : library member,
student
Events : arrival, leaving,
request
Identify Class Attributes &
Operations
Book
ISBNNo : String Title : String Author : String Status : String
select()
isAvailable() updateStatus()
Attributes
Operations
Characteristic of a
class
Simple noun or noun
phrases
Must be unique
within class
Value that the
property may hold in objects of that class
What the class can do /
What the class should do
Operations are used to interact with objects and classes
Operation signature
Optional argument
list
Return class
Relationship
Why do we need Relationship
All system encompass many classes and
objects
Objects contribute to the behavior of a system
by collaborating with one another
Collaboration is accomplish through relationships
Two important type of relationship during
analysis
Association
Represent relationship between objects of classes
Multiplicity Association
Number of instance of one class related to one
instance of the other class
Multiplicity indicator
Many - *
Exactly one - 1
Zero or more - 0 .. * One or more - 1 .. * Zero or one - 0 .. 1
Inheritance
Hierarchy abstraction where subclass
inherits from one or more superclass
Subclass inherits attributes, operations
and relationships
Subclass may have additional attributes,
operations or relationship
How to find inheritance?
Aggregation
Known as part-of relationship
A whole class related to its parts Association or Aggregation ?
If two object tightly bound by a whole part
relationship : Aggregation
If two object considered independent even
Example of Aggregation
ATM Panel Card Reader ATM Card
Country States
1 1
Country and States are tightly coupled.
States cannot function on its own if it taken away from country.
1 1 1 0 ..1
Object Interactions
To show dynamic behavior of the system
Also known as Sequence Diagram
Interaction between objects is modeled
using interaction diagram.
Show how messages passed between objects
Object Interactions
(Continued)aMember:BookBorrower
theLibraryMember:
LibraryMember theCopy:Copy theBook:Book
borrow(theCopy)
1: okToBorrow
2: borrow
Changes In System : State
Diagram
State of book object may change when
a copy of book is successfully book
borrowable not borrowable
There is a copy
available in the library All copies are out on loan or reserved
not borrowable borrowable
returned()
returned()
borrowed() [last copy]
Deliverables from Unified Modeling Language Approach OOA
Use Case Diagram
Sequence Diagram
Class Diagram
Object-Oriented Design
Detailed specifications of the following:
Subsystems or class categories
Partitioning the system, providing interfaces,
interactions, and mapping to targeted system
Class definitions
structure or representation
behaviour or operations
implementation algorithms
Object-Oriented Design
(Continued) Class relationships
Containment
Referencing
Aggregation
Inheritance
Object diagrams and object relationships
Descriptions of how objects interact
Object-Oriented Design
(Continued) State transition
Extends state transition diagrams in analysis
Timing diagrams
Extends timing diagrams in analysis
Designing algorithms
implementation algorithms and logic
Physical compilation units
UML Approach to OOD
Object Oriented Design
Object Oriented Design
System DesignSystem Design Object DesignObject Design
Software Architecture Software
Architecture DescriptionObject Object
System Design
Partition the Analysis Model
Refine analysis objects using inheritance, pattern and
encapsulation
Package into subsystem or modules
Can be characterized by responsibility
Design artifact may include Refined class diagram
Interaction, activity component & deployment diagram State models
Composed classes into packages. Composition can be done
base on
Use cases
System Design
(continued)
Concurrency and Subsystem Allocation
Assign concurrency if classes are active at the same
time
Implement on the same processor hardware
Concurrent is defined by examining the state diagram Establish thread for active object
Thread control continues when it sends message to another
object and wait for responses
Isolate these thread controls
System Design
(Continued)
Task Management Component
How the task initiated Common
Event driven
• Interrupt from outside source (Processor, sensor etc)
Clock driven
• Interrupt from system clock
Determine the task priority and criticality
High priority task must have immediate access to the
resources
High critical task must operate continually even if
System Design
(continued)
User Interface Component
Define system menu and sub functions available for
the menu
Data Management Component
Data management for critical application Layered design
Creation of infrastructure for storage and retrieval Use database, files, shared memory
Design the attribute and operation to manage data
System Design
(continued)
User Interface Component
Define system menu and sub functions available for
the menu
Data Management Component
Data management for critical application Layered design
Creation of infrastructure for storage and retrieval Use database, files, shared memory
Design the attribute and operation to manage data
Resource Management Component
Activity Diagram
Activity diagram
Activities coordination
To show how an operation can be
implemented
Useful when an operation has to achieve a
number of different things
Record dependencies between activities
Which thing can happen in parallel
Find book on shelf Wait in queue
Record return Put book back on shelf Record
borrowing
Prepare for
[borrower]
[returner]
[returning]
[borrowing]
member librarian
Object Design
Object Description
Establish object interface
Define message the object can receive
Operation the object can perform when it receives the
message
Implementation details Objects private parts
Internal details about data structure Details about the operation
Algorithms and Data Structure
Component Model
Component
Standard building unit that is used to develop an
application
Types of component
Source code (e.g: file containing code of the class) Has to be available when compiled
Binary object code (e.g: class library) Depends on any object code
Must be linked to form an executable program
Executable application (e.g: the client/server,
database manager)
A component diagram showing compile time dependencies
streams.o <<library>>
MyIO
MyApp <<executable>>
<<compile>> <<link>>
component
Deployment Model
Deployment diagram shows
Physical communication links between hardware items Machines, printers and other resources
Relationship between physical machines and processes What runs where
shillay:Workstation
OXO:GameEngine
P1:PlayerInterface
craro:PC
P2:PlayerInterface
<<LAN>>
Node
•Processor, capable of running the software component
Deliverables from UML
Approach to OOD
Class Diagram (Refined)
State Transition Diagram (Refined)
Component Diagram
References
“Software Engineering: A Practitioner’s Approach” 5th Ed. by Roger S.
Pressman, Mc-Graw-Hill, 2001
“Object-Oriented Modeling and Design” by James Rumbaugh et al,
Prentice Hall, 1991
“Object Orientation” by Setrag Khoshafian & Razmik Abnous, John
Wiley & Sons, 1995
“Teach Your Self UML in 24 hours” by Joseph Schmuller, Sams
Publication, 2001
“Mastering UML with Rational Rose” by Wendy Boggs and Michael
Boggs, Sybex Inc, 2000
“Using UML Software Engineering With Objects and Components” by
