Introduction to OOA and UML

Business Analysis
Training for Beginners
Introduction to OOA and UML

Classification: Restricted
Agenda
• Elements, purpose and example of UML Diagrams :
• Use Case Diagram
• Class Diagram
• Sequence Diagram
• Collaboration Diagram
• State Diagram
• Activity Diagram

Modeling
• Describing a system at a high level of abstraction
– A model of the system
– Used for requirements and specifications
• Is it necessary to model software systems?

What is UML?
• UML stands for “Unified Modeling Language”
• It is a industry-standard graphical language for specifying, visualizing,
constructing, and documenting the artifacts of software systems
• The UML uses mostly graphical notations to express the OO analysis and
design of software projects.
• Simplifies the complex process of software design

Why UML for Modeling
• Use graphical notation to communicate more clearly than natural
language (imprecise) and code(too detailed).
• Help acquire an overall view of a system.
• UML is not dependent on any one language or technology.
• UML moves us from fragmentation to standardization.

Overview of UML Diagrams
Overview of UML DiagramsStructural
: element of spec. irrespective of time
o Class
o Component
o Deployment
o Object
o Composite structure
o Package
Behavioral
: behavioral features of a system / business
process
o Activity
o State machine
o Use case
o Interaction
Interaction
: emphasize object interaction
o Communication(collaborati
on)
o Sequence
o Interaction overview
o Timing

Types of UML Diagrams
• Use Case Diagram
• Class Diagram
• Sequence Diagram
• Collaboration Diagram
• State Diagram
This is only a subset of diagrams … but are most widely used

Use Case Diagram
• Used for describing a set of user scenarios
• Mainly used for capturing user requirements
• Work like a contract between end user and software developers

Use Case Diagram (core components)
Actors: A role that a user plays with respect to the system, including human
users and other systems. e.g., inanimate physical objects (e.g. robot); an
external system that needs some information from the current system.
Use case: A set of scenarios that describing an interaction between a user
and a system, including alternatives.
System boundary: rectangle diagram representing the boundary between
the actors and the system.

Use Case Diagram (core relationship)
Association: communication between an actor and a use case;
Represented by a solid line.
Generalization: relationship between one general use case and a
special use case (used for defining special alternatives)
Represented by a line with a triangular arrow head toward the parent
use case.

Generalization

Include: a dotted line labeled <<include>> beginning at base use case and
ending with an arrows pointing to the include use case. The include
relationship occurs when a chunk of behavior is similar across more than one
use case. Use “include” in stead of copying the description of that behavior.
<<include>>
Extend: a dotted line labeled <<extend>> with an arrow toward the base case.
The extending use case may add behavior to the base use case. The base class
declares “extension points”.
<<extend>>

Use Case Diagrams
Library System
Borrow
Order Title
Fine Remittance
Client
Employee
Supervisor
Boundary
Actor
Use Case

Use Case Diagrams

Types of Actor
Actors
Primary
Actor
Secondary Actor

Types of Actor

Exercise

Use Case Specification

Use Cases for the Exercise

Actors for the Exercise

Relationship between the actors

• Used for describing structure and behavior in the use cases
• Provide a conceptual model of the system in terms of entities and their
relationships
• Used for requirement capture, end-user interaction
• Detailed class diagrams are used for developers
Class diagram

A collection of similar objects is a class. And an object is an instance of a class.
What is a Class?

Class representation
• Each class is represented by a rectangle subdivided into three
compartments
• Name
• Attributes
• Operations
• Modifiers are used to indicate visibility of attributes and operations.
• ‘+’ is used to denote Public visibility (everyone)
• ‘#’ is used to denote Protected visibility (friends and derived)
• ‘-’ is used to denote Private visibility (no one)
• By default, attributes are hidden and operations are visible.

An example of Class
Account_Name
- Customer_Name
- Balance
+addFunds( )
+withDraw( )
+transfer( )
Name
Attributes
Operations

• Super Class
• Parent Class
• Generalized Class
• Specialized Class
• Sub Class
• Child Class
Types of Classes

Animal
Amphibian Mammal Reptile
Horse
Example
Child Class
of Animal
Child Class
of Animal
Child Class
of Mammal
Super Class
of horse
Parent Class
of Mammal
Sub Class of
Animal

OO Relationships
• There are two kinds of Relationships
• Generalization (parent-child relationship)
• Association (one object to another object relationship)
• Associations can be further classified as
• Aggregation
• Composition

OO Relationships : Generalization
Subtype2
Supertype
Subtype1
• Generalization expresses a
parent/child relationship
among related classes.
• Used for abstracting details in
several layers
Regular
Customer
Loyalty
Customer
Customer
Example
:
Regular
Customer
Loyalty
Customer
Customeror:

OO Relationships : Association
• Represent relationship between instances of classes
• Student enrolls in a course
• Courses have students
• Courses have exams
• Etc.
• Association has two ends
• Role names (e.g. enrolls)
• Multiplicity (e.g. One course can have many students)
• Navigability (unidirectional, bidirectional)

University Person
1
0..1
*
*
Multiplicity
Symbol Meaning
1 One and only one
0..1 Zero or one
M..N From M to N (natural language)
* From zero to any positive integer
0..* From zero to any positive integer
1..* From one to any positive integer
teacheremployee
Role
“A given university groups many people;
some act as students, others as teachers.
A given student belongs to a single
university; a given teacher may or may not
be working for the university at a particular
time.”
student
Association: Multiplicity and Roles

Class Diagram

OO Relationships : Composition
Class W
Class P1 Class P2
Whole Class
Part Classes
Automobile
Engine Transmission
Example
Composition: expresses a relationship among instances of
related classes. It is a specific kind of Whole-Part
relationship.
It expresses a relationship where an instance of the
Whole-class has the responsibility to create and initialize
instances of each Part-class.
It may also be used to express a relationship where instances
of the Part-classes have privileged access or visibility to
certain attributes and/or behaviors defined by the Whole-
class.
Composition should also be used to express relationship
where instances of the Whole-class have exclusive access to
and control of instances of the Part-classes.
Composition should be used to express a relationship where
the behavior of Part instances is undefined without being
related to an instance of the Whole. And, conversely, the
behavior of the Whole is ill-defined or incomplete if one or
more of the Part instances are undefined.
[From Dr.David A. Workman]

OO Relationships : Composition
[From Dr.David A. orkman]
Class C
Class E1 Class E2
AGGREGATION
Container Class
Containee Classes
Bag
Apples Milk
Example
Aggregation: expresses a relationship among
instances of related classes. It is a specific kind of
Container-Containee relationship.
It expresses a relationship where an instance of
the Container-class has the responsibility to hold
and maintain instances of each Containee-class
that have been created outside the auspices of the
Container class.
Aggregation should be used to express a more
informal relationship than composition expresses.
That is, it is an appropriate relationship where the
Container and its Containees can be manipulated
independently.
Aggregation is appropriate when Container and
Containees have no special access privileges to
each other.

Aggregations vs. Composition
• Composition is really a strong form of aggregation
• components have only one owner
• components cannot exist independent of their
owner
• components live or die with their owner
e.g. Each car has an engine that can not be
shared with other cars.
•Aggregations may form "part of" the aggregate, but may not be
essential to it. They may also exist independent of the aggregate.
e.g. Apples may exist independent of the bag.

Interaction Diagrams
A Sequence diagram is an interaction diagram that shows how objects
operate with one another and in what order.
• They're also called event diagrams.
• A sequence diagram is a good way to visualize and validate various
runtime scenarios.
• These can help to predict how a system will behave and to discover
responsibilities a class may need to have in the process of
modeling a new system

Sequence Diagrams

Class Roles or Participants
Class roles describe the way an object will behave in context. Use the UML
object symbol to illustrate class roles, but don't list object attributes.
Basic Sequence Diagram Symbols and Notations

Activation or Execution Occurrence
Activation boxes represent the time an object needs to complete a task.
When an object is busy executing a process or waiting for a reply message,
use a thin gray rectangle placed vertically on its lifeline.

Messages
Messages are arrows that represent communication between objects. Use
half-arrowed lines to represent asynchronous messages. Asynchronous
messages are sent from an object that will not wait for a response from the
receiver before continuing its tasks..

Lifelines
Lifelines are vertical dashed lines that indicate the object's presence over
time.

Destroying Objects
Objects can be terminated early using an arrow labeled "<< destroy >>" that
points to an X. This object is removed from memory. When that object's
lifeline ends, you can place an X at the end of its lifeline to denote a
destruction occurrence.
Loops
A repetition or loop within a sequence diagram is depicted as a rectangle.
Place the condition for exiting the loop at the bottom left corner in square
brackets [ ].

Types of Messages in Sequence Diagram
Synchronous Message
A synchronous message requires a response before the interaction can
continue. It's usually drawn using a line with a solid arrowhead pointing
from one object to another.

Asynchronous Message
Asynchronous messages don't need a reply for interaction to continue. Like
synchronous messages, they are drawn with an arrow connecting two
lifelines; however, the arrowhead is usually open and there's no return
message depicted.

Caller Phone Recipient
Picks up
Dial tone
Dial
Ring notification Ring
Picks up
Hello
Sequence Diagram (make a phone call)

Sequence Diagram : Object interaction
Self-Call: A message that an
Object sends to itself.
Condition: indicates when a
message is sent. The message is
sent only if the condition is true.
Iteration
Condition
A B
Synchronous
Asynchronous
Transmission
delayed
Self-Call
[condition]
remove()
*[for each]
remove()

Sequence Diagrams – Object Life Spans
• Creation
• Create message
• Object life starts at that point
• Activation
• Symbolized by rectangular stripes
• Place on the lifeline where object is
activated.
• Rectangle also denotes when object
is deactivated.
• Deletion
• Placing an ‘X’ on lifeline
• Object’s life ends at that point
Activation
bar
A
B
Create
X
Deletion
Return
Lifeline

Sequence Diagrams – Example

The second interaction diagram is collaboration diagram. It shows the
object organization. Here in collaboration diagram the method call
sequence is indicated by some numbering technique.
Collaboration Diagrams

Collaboration Diagram : Example

• Shows the relationship between objects and the order of messages passed
between hem.
• The objects are listed as rectangles and arrows indicate the messages being
passed
• The numbers next to the messages are called sequence numbers. They
show the sequence of the messages as they are passed between the objects.
• Convey the same information as sequence diagrams, but focus on object
roles instead of the time sequence.
Interaction Diagrams : Collaboration diagrams

State Diagrams: (Billing Example)
State Diagrams show the sequences of states an object goes through during
its life cycle in response to stimuli, together with its responses and actions;
an abstraction of all possible behaviors.
Unpaid
Start End
Paid
Invoice created paying Invoice destroying

State Diagrams: (Traffic light example)
Yellow
Red
Green
Traffic Light
State
Transition
Event
Star
t

Activity Diagram
Overview
• Activity diagram is another important diagram in UML to describe dynamic
aspects of the system.
• Activity diagram is basically a flow chart to represent the flow form one
activity to another activity. The activity can be described as an operation of
the system.
• So the control flow is drawn from one operation to another. This flow can
be sequential, branched or concurrent. Activity diagrams deals with all type
of flow control by using different elements like fork, join etc.

Purpose of an Activity Diagram
• Draw the activity flow of a system.
• Describe the sequence from one activity to another.
• Describe the parallel, branched and concurrent flow of the system.

Elements of Activity Diagram

Activity Diagram : Example

• Agile Methodology
• User Story – Introduction
• Format of User Story
• Usage of User Story
• Example of User Story
Topics to be covered in next session

Thank you

Introduction to OOA and UML

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