INTRODUCTION
CLASS DIAGRAM
• A class diagram shows the existence of classes and their relationships in the logical view of a system
• UML modeling elements in class diagrams are:
– Classes, their structure and behavior.
– relationships components among the classes like association, aggregation, composition, dependency and inheritance
– Multiplicity and navigation indicators
– Role names or labels.
Basic two types of classes
Concrete classes
• A concrete class is a class that is instantiable; that is it can have different instances.
• Only concrete classes may be leaf classes in the inheritance tree.
Abstract classes
• is a class that has no direct instance but whose descendants classes have direct instances.
• can define the protocol for an operation without supplying a corresponding method we call this as an abstract operation.
operation defines the form of operation, for which each concrete subclass should provide its own implementation
Types of Relationships between classes
• Association
• Aggregation
• Composition
• Inheritance
• Dependency
• Instantiation
