Consider ticket-selling domain model:

• Customer, Reservation, Ticket, and Performance are classes.

• Customers may have many reservations.

• Each reservation is made by one customer.

• Reservations are of two kinds:

  • subscription series

  • individual reservations.

Class diagram for ticket box application:

Subscription reservation can reserve several tickets.

Individual reservation is capable of reserving only a single ticket.

Every performance has many tickets available.

Each ticket has unique seat number.

A performance can be identified by a show, a date, and time.

Class diagram for ticket box application:

A class defines a set of objects that have state and behavior.

Attributes store data values such as members and strings.

Object behavior is determined by its operations.

The lifetime of an object is described by a state machine attached to a class.

An interface is the description of behavior of objects without implementation or state.

One or more classes or components may realize an interface.

Class that implements the interface implements the operations found in the interface.

Primitive types include numbers and strings.

Primitive types are passed around by value.

Operations may return data values as results.

Association provides description of a connection among instances of classes.

Most common kind of association is a binary association between a pair of classes.

Associations carry information about relationships among objects in a system.

As a system executes, links among objects are created and destroyed.

Associations are the glue that ties a system together.

Without associations, there are nothing but isolated classes that don't work together.

Most important property of association is multiplicity.

Multiplicity specifies how many instances of one class can be related to one instance of the other class.

A relationship between classes involved in inheritance and polymorphic behavior.

For example,

• A mortgage is a more specific kind of loan.

• A mortgage keeps the basic characteristics of a loan, but adds additional characteristics, such as a house as security for the loan.

Generalization enables polymorphic operations.

Realization relationship is specified between interface and its implementation.

The realization relationship is like generalization in which only behavior specification is inherited rather than structure of attributes or implementation.