Session 3 Understand and Use Object Oriented Methods

Review OOAD refers to the development of systems with the base concept of objects and classes UML is a modeling tool used in Information systems Technical systems Embedded systems Distributed systems System software Business Systems SDLC refers to different phases in the software development process

OOAD refers to the development of systems with the base concept of objects and classes

UML is a modeling tool used in

Information systems

Technical systems

Embedded systems

Distributed systems

System software

Business Systems

SDLC refers to different phases in the software development process

Objectives Discuss the class diagram and object diagram Represent the relationships between classes Discuss the concept of object Model Identify classes during analysis

Discuss the class diagram and object diagram

Represent the relationships between classes

Discuss the concept of object Model

Identify classes during analysis

Class and Object Class - A class is a description of a group of objects with common properties (attributes), behavior (Operations), relationships, and semantic Object - An object represents an entity, either physical, conceptual, or software

Class - A class is a description of a group of objects with common properties (attributes), behavior (Operations), relationships, and semantic

Object - An object represents an entity, either physical, conceptual, or software

Class Diagram-1 Class Object

Class Diagram-2 Class Names Class Attributes Class Methods Constraints Comment

Class Names

Class Attributes

Class Methods

Constraints

Comment

Representation of Relationship Multiplicity - Multiplicity defines how many objects participate in a relationship

Multiplicity - Multiplicity defines how many objects participate in a relationship

Multiplicity & Navigation Student Schedule Navigation Multiplicity 0..* 1

Aggregation An aggregation is a stronger form of relationship where the relationship is between a whole and its parts Student Schedule Aggregation Whole Part

An aggregation is a stronger form of relationship where the relationship is between a whole and its parts

Aggregation-Composition Composition is a form of aggregation with strong ownership and coincident lifetimes of the part with the aggregate Student Schedule Aggregation Whole Part

Composition is a form of aggregation with strong ownership and coincident lifetimes of the part with the aggregate

Aggregation- Dependency A dependency relationship is a weaker form of relationship

A dependency relationship is a weaker form of relationship

Aggregation-Generalization A specialization/generalization relationship is one, in which objects of the specialized element (the child) are substitutable for objects of the generalized element (the parent) Superclass Subclass

A specialization/generalization relationship is one, in which objects of the specialized element (the child) are substitutable for objects of the generalized element (the parent)

Superclass

Subclass

Association Association is a connection between classes Professor University Professor University Works for Class Association Name Role Names Employer Employee

Association is a connection between classes

Constraints of Association An association may have a name that is placed on, or adjacent to the association path The name of the association should reflect the purpose of the relationship and be a verb phrase; the name of an association can be omitted, particularly if roles names are used. Names like “has” and “contains should be avoided”, as they add no information about what the relationships are between the classes. Each end of an association is a role specifying the face that a class plays in the association (not a constraint). Each role must have a name, and the role names must be unique. The role name should be a noun indicating the associated object’s role in relation to the associating object. The use of association names and role names are mutually exclusive: one should not use both an association name and role name. For each association, it needs to decide as to which conveys more information.

An association may have a name that is placed on, or adjacent to the association path

The name of the association should reflect the purpose of the relationship and be a verb phrase; the name of an association can be omitted, particularly if roles names are used. Names like “has” and “contains should be avoided”, as they add no information about what the relationships are between the classes.

Each end of an association is a role specifying the face that a class plays in the association (not a constraint). Each role must have a name, and the role names must be unique. The role name should be a noun indicating the associated object’s role in relation to the associating object.

The use of association names and role names are mutually exclusive: one should not use both an association name and role name. For each association, it needs to decide as to which conveys more information.

Association Classes

Qualified Association Theatre Seat 1 99 Theatre Seat 1 Row {1,2,…9} Column {1,2,..11} 1

Recursive Association

Inheritance and Generalization-1

Inheritance and Generalization-2 The mechanism for sharing attributes and operations using the principle of generalization is referred to as inheritance

The mechanism for sharing attributes and operations using the principle of generalization is referred to as inheritance

Same Association or Aggregation

Interface

Object Model Language independent Notation allowing the specification of classes, their data or attributes (private) and methods (public), inheritance This diagram depicts the structural relationship and functional behavior of the classes

Language independent

Notation allowing the specification of classes, their data or attributes (private) and methods (public), inheritance

This diagram depicts the structural relationship and functional behavior of the classes

Nouns in problem statement Knowledge of the problem domain Use Cases Physical entities Devices Events Roles played Operational procedures Sites Organisational units How to Identify Classes? Tangible things Events Roles played Interactions Location Organizational Units The Requirements statement Use Cases Application experts Studying the system Similar systems Previous systems

Nouns in problem statement

Knowledge of the problem domain

Use Cases

Physical entities

Devices

Events

Roles played

Operational procedures

Sites

Organisational units

Tangible things

Events

Roles played

Interactions

Location

Organizational Units

The Requirements statement

Use Cases

Application experts

Studying the system

Similar systems

Previous systems

Candidate Classes

Summary A class icon is a rectangle with three sections within it Association is a connection between classes An interface is a collection of operations that are used to specify a service of a class or a component Object Model generally deals with classes

A class icon is a rectangle with three sections within it

Association is a connection between classes

An interface is a collection of operations that are used to specify a service of a class or a component

Object Model generally deals with classes