DEV475 Mastering Object-Oriented Analysis and Design with UML ...

Module 2 - Concepts of Object OrientationWhat Is a Subsystem?What Is a Subsystem?• A combination of a package (can contain othermodel elements) and a class (has behavior)• Realizes one or more interfaces which defineits behaviorSubsystemRealizationInterfaceSubsystemNameInterface1OO Principles: Encapsulation and ModularityMastering Object Oriented Analysis and Design with UMLCopyright © 2003 Rational Software, all rights reserved 33(stay tuned for realization relationships)A subsystem is a model element that has the semantics of a package, such that it cancontain other model elements, and a class, such that it has behavior. (The behavior ofthe subsystem is provided by classes or other subsystems it contains.) A subsystemrealizes one or more interfaces, which define the behavior it can perform.From the UML User’s Guide (Booch, 1999): A subsystem is “a grouping of elements ofwhich some constitute a specification of the behavior offered by the other containedelements.”A subsystem may be represented as a stereotyped package.The realization relationship will be discussed later in this module.2 - 33