What Are the Benefits of Packages?

• Enforced Information Hiding
• Object-Oriented Design
• Top-Down Design
• Object Persistence
• Guaranteeing Transaction Integrity
• Performance Improvement

A Booch diagram for a package:

All of the boxes that lie completely inside the box are private elements, defined only within the body of the package. Boxes that lie on the boundary of the box are public elements, defined in the package specification and implemented (if programs) in the package body. An external program can make direct references only to those package elements that lie on the boundary. But any package element, whether wholly inside the boundary or straddling that line, can reference any other package element.

A boundary in the package delineates that which is publicly available and that which is private or hidden from view. It has particularly important and valuable consequences for data structures defined in a package.