A class diagram describes the structure of a system by showing classes, attributes, operations, and relationships among classes. A class represents a set of objects that share attributes, operations, and semantics. It is drawn as a rectangle with the class name, attributes, and operations in compartments. Relationships include dependencies, generalizations, and associations. Generalization connects a subclass to a superclass, allowing encapsulation and specialization. Associations link communicating classes, with multiplicity indicating the number of instances in the relationship.

1. Class Diagram & Object Diagram
ATA.USAMA
AMP/IT/2015/F/0018

2. What is a Class Diagram?
 A Class Diagram is a diagram describing the structure
of a system.
 It consists the :
 Classes.
 Attributes.
 Operations.
 Relationships among the classes.

3. Classes
 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 , designated compartments.
ClassName
attributes
operations

4. Class Names
 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.
ClassName
attributes
operations

5. Class Attributes
should include all fields of the object.
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.
Example;
 a Person’s age can be computed from his birth date.
/ age : Date
Person
name : String
address : Address
birthdate : Date
/ age : Date
ssn : Id

6. Class Attributes (Cont..)
 Attributes can be:
 + public.
 # protected.
 - private.
 / derived.
Person
+ name : String
# address : Address
# birthdate : Date
/ age : Date
- ssn : Id

7. Class Operations
 Operations describe the class behavior and appear in
the third compartment.
Person
name : String
address : Address
birthdate : Date
ssn : Id
eat
sleep
work
play

8. Relationships
There are three types of relationships you can
set up between classes.
Dependencies
Generalizations
Associations

9. Dependency Relationships
 A dependency indicates a semantic relationship
between two or more elements.
 Symbolized by dotted line.

10. Generalization Relationships
 A generalization connects a subclass to its superclass.
 Generalization provides the capability to create
supper classes that encapsulate structure and behavior
common to several classes.
 specialization provides the ability to create subclasses
that represent refinement to the supper-class.t.

11. Example :

12. Association Relationships
 If two classes in a model need to communicate with each
other, there must be link between them.
Here , an association is instructs
Instructor Student
instructs

13. Association Relationships(Cont..)
 We can indicate the multiplicity of an association by
adding multiplicity adornments to the line denoting the
association.
The example indicates that a Student has one or more
Instructors:
Student Instructor
1..*

14. Thank You
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