Class diagram- UML diagram

Duration : 3 hrs
1
Ramakant Soni
Assistant Professor
Dept. of Computer Science
B K Birla Institute of Engineering & Technology, Pilani, India
Ramakant Soni @ BKBIET PIlani

Class Diagram Overview
Class diagram is one type of UML structure diagram
which shows structure of the designed system at the
level of classes and interfaces, shows their features,
constraints and their relationships - associations,
generalizations, dependencies, etc.
Ramakant Soni @ BKBIET PIlani 2

ClassName
attributes
A class is a description of a set of objects
that share the same attributes, operations,
relationships, and semantics.
Graphically, a class is rendered as a
rectangle, usually including its name,
attributes, and operations in separate,
operations
attributes, and operations in separate,
designated compartments.

ClassName
attributes
The name of the class is the only required tag in
the graphical representation of a class. It
always appears in the top-most compartment.
operations

Person
name : String
address : Address
birthdate : Date
An attribute is a named property of a class
that describes the object being modeled.
In the class diagram, attributes appear in thebirthdate : Date
ssn : Id
In the class diagram, attributes appear in the
second compartment just below the name-
compartment.

Person
name : String
address : Address
Attributes are usually listed in the form:
attributeName : Type
A derived attribute is one that can be
computed from other attributes, but doesn’t
actually exist.
address : Address
birthdate : Date
/ age : Date
ssn : Id
For example, a Person’s age can be
computed from his birth date. A derived
attribute is designated by a preceding ‘/’ as
in:
/ age : Date

Person
+ name : String
# address : Address
Attributes can be:
+ public
# protected
- private
# address : Address
# birthdate : Date
/ age : Date
- ssn : Id
- private
/ derived

Person
name : String
address : Address
birthdate : Datebirthdate : Date
ssn : Id
Eat()
Sleep()
Work()
Play()
Operations describe the class behavior
and appear in the third compartment.

A class may also include its responsibilities in a class diagram.
A responsibility is a contract or obligation of a class to perform a
particular service.
SmokeAlarm
Responsibilities
-- sound alert and notify guard station
when smoke is detected.
-- indicate battery state

In UML, object interconnections (logical or physical), are modeled as
relationships.
There are five kinds of relationships in UML:
• dependencies
• generalizations
• associations
•Inheritence
•realization

A dependency indicates a semantic relationship between two or
more elements. The dependency from CourseSchedule to Course
exists because Course is used in both the add and remove operations
of CourseSchedule.
CourseSchedule
add(c : Course)
remove(c : Course)
Course

Person
A generalization connects a subclass to its
super class.
It denotes an inheritance of attributes and
behavior from the super class to thebehavior from the super class to the
subclass and indicates a specialization in
the subclass of the more general super
class.
Student

Student
UML permits a class to inherit from multiple superclasses, although some
programming languages (e.g., Java) do not permit multiple
inheritance.
Employee
TeachingAssistant

If two classes in a model need to communicate with each other, there
must be link between them.
An association denotes that link.
InstructorStudent

Class diagram- UML diagram

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