Object oriented programming language in software engineering

1
DEPARTMENT OF COMPUTER SCIENCE
AND ENGINEERING
(2016-17)
OBJECT ORIENTED ANALYSIS AND DESIGN
III B. Tech II Sem
UNIT-1

What is UML?
 UML stands for “Unified Modeling Language”
 It is a industry-standard graphical language .
 UML is a pictorial language used to make software blue prints
 It is used for specifying, visualizing, constructing, and documenting the
artifacts of software systems
 UML is different from the other common programming languages
 It uses mostly graphical notations.
 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.
 Tools can be used to generate code in various languages using UML diagrams
 UML is not dependent on any one language or technology.
 A picture is worth than thousand words
 UML can be defined as a simple modeling mechanism to model all possible
practical systems in today’s complex environment.

conceptual model of UML
 It is a model which is made of concepts and their relationships.
 It is the first step before drawing a UML diagram.
 It helps to understand the entities in the real world and how they interact
with each other
 It can be mastered by learning the following three major elements:
UML building blocks
Rules to connect the building blocks
Common mechanisms of UML

Object oriented concepts
 object contains both data and methods that control the data.
 The data represent the state of the object
 Data can also describe the relationships between this object
and other objects
 objects are the real world entities

Object oriented concepts
 Every object belongs to (is an instance of) a class
 An object may have fields, or variables
 The class describes those fields
 An object may have methods
 The class describes those methods
 A class is like a template, or cookie cutter
 You use the class’s constructor to make objects

Example: A “Rabbit” object
 You could (in a game, for example) create an object
representing a rabbit
 It would have data:
 How hungry it is
 How frightened it is
 Where it is
 And methods:
 eat, hide, run, dig

Concept: Classes form a hierarchy
 Classes are arranged in a tree like structure called a hierarchy
 The class at the root is named Object
 Every class, except Object, has a super class
 A class may have several ancestors, up to Object
 When you define a class, you specify its super class
 Every class may have one or more subclasses

Fundamental concepts of object oriented world
 Objects: Objects represent an entity and are the basic building block.
 Class: Class is the blue print of an object.
 Abstraction: Abstraction represents the behavior of an real world entity.
 Encapsulation: Encapsulation is the mechanism of binding the data together and
hiding them from outside world.
 Inheritance: Inheritance is the mechanism of making new classes from existing one.
 Polymorphism: It defines the mechanism to exists in different forms.

Kinds of access
 Java provides four levels of access:
 public: available everywhere
 protected: available within the package (in the same
subdirectory) and to all subclasses
 [default]: available within the package
 private: only available within the class itself
 The default is called package visibility

OO Analysis and Design
 it is the investigation of objects. Design means collaboration of identified
objects.
 identifying the objects their relationships are identified and finally the
design is produced
 Identifying the objects of a system.
 Identify their relationships.
 OO Analysis --> OO Design --> OO implementation using OO languages

Building blocks of UML
 The building blocks of UML can be defined as:
 Things
 Relationships
 Diagrams

Things
 Things are the most important building blocks of UML.
Things can be:
 Structural
 Behavioral
 Grouping
 Annotational

Structural things
 The Structural things define the static part of the model.
 They represent physical and conceptual elements.
Class:
 Class represents set of objects having similar responsibilities.
Interface:
 Interface defines a set of operations which specify the responsibility
of a class
Collaboration:
 Collaboration defines interaction between elements.

Structural things
Use case:
 Use case represents a set of actions performed by a system for
a specific goal.
Component:
 Component describes physical part of a system.
Node:
 A node can be defined as a physical element that exists at run
time.

Behavioral things
 It consists of the dynamic parts of UML models.
Interaction:
 It is defined as a behavior that consists of a group of messages
exchanged among elements to accomplish a specific task.
State machine:
 It is useful when the state of an object in its life cycle is
important. It defines the sequence of states an object goes
through in response to events.

Grouping things
 Grouping things can be defined as a mechanism to group
elements of a UML model together. There is only one grouping
thing available:
Package:
 Package is the only one grouping thing available for gathering
structural and behavioral things.

Annotational things
 Annotational things can be defined as a mechanism to
capture remarks, descriptions, and comments of UML model
elements.
Note
 It is the only one Annotational thing available.
 A note is used to render comments, constraints etc of an UML
element.

Relationships
 It shows how elements are associated with each other and this
association describes the functionality of an application.
There are four kinds of relationships available.
Dependency:
 Dependency is a relationship between two things in which
change in one element also affects the other one.
Association:
 Association is basically a set of links that connects elements of
an UML model. It also describes how many objects are taking
part in that relationship.

Relationships
Generalization:
 Generalization can be defined as a relationship which
connects a specialized element with a generalized element. It
basically describes inheritance relationship in the world of
objects.
Realization:
 Realization can be defined as a relationship in which two
elements are connected. One element describes some
responsibility which is not implemented and the other one
implements them. This relationship exists in case of
interfaces.

Object oriented programming language in software engineering

Types of UML Diagrams
 UML includes the following nine diagrams
 Class diagram
 Object diagram
 Use case diagram
 Sequence diagram
 Collaboration diagram
 Activity diagram
 Statechart diagram
 Deployment diagram
 Component diagram

Structural Diagrams
 They represent the static aspect of the system. These static aspects
represent those parts of a diagram which forms the main
structure and therefore stable
The four structural diagrams are:
 Class diagram
 Object diagram
 Component diagram
 Deployment diagram

Behavioral diagrams
 Any system can have two aspects, static and dynamic.
 A model is considered as complete when both the aspects are
covered fully.
 It basically capture the dynamic aspect of a system.
 Dynamic aspect can be further described as the changing/moving
parts of a system.
UML has the following five types of behavioral diagrams:
 Use case diagram
 Sequence diagram
 Collaboration diagram
 Statechart diagram
 Activity diagram

Classes
 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

OO Relationships
 There are two kinds of Relationships
 Generalization (parent-child relationship)
 Association (student enrolls in course)
 Associations can be further classified as
 Aggregation
 Composition

Subtype2
Supertype
Subtype1
OO Relationships: Generalization
- 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
Customer
or:

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)

Association: Multiplicity and Roles
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
teacher
employer
Role
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: Model to Implementation
Class Student {
Course enrolls[4];
}
Class Course {
Student have[];
}
Student Course
enrolls
has
* 4

OO Relationships: Composition
Class W
Class P1 Class P2
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.
Whole Class
Part Classes
Automobile
Engine Transmission
Example
[From Dr.David A. Workman]

OO Relationships: Aggregation
Class C
Class E1 Class E2
AGGREGATION
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.
Container Class
Containee Classes
Bag
Apples Milk
Example
[From Dr.David A. Workman]

Aggregation vs. Composition
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.

Object oriented programming language in software engineering

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