Object: many definitions for an object have been proposed, most of which are quite similar, In this book we define an object as something real or abstract about which we store data those operation that manipulate the data Examples of these include an invoice, an account, a sensor, a software design, a car and an organization. It is possible for an object of be composite, that is, composed of other object Every object is defined by its list of attributes (or data). An attributes describes some aspect of the object to which it belongs. For example, a customer entity might have attributes like account number, name, address, phone number and so on.