The Unified Modeling Language User Guide SECOND EDITION [Electronic resources] نسخه متنی

Chapter 9. Advanced Classes

In this chapter

• Classifiers, special properties of attributes and operations, and different kinds of classes

• Modeling the semantics of a class

• Choosing the right kind of classifier

Classes are indeed the most important building block of any object-oriented system. However, classes are just one kind of an even more general building block in the UMLclassifiers. A classifier is a mechanism that describes structural and behavioral features. Classifiers include classes, interfaces, datatypes, signals, components, nodes, use cases, and subsystems.

Classifiers (and especially classes) have a number of advanced features beyond the simpler properties of attributes and operations described in the previous part: You can model multiplicity, visibility, signatures, polymorphism, and other characteristics. In the UML, you can model the semantics of a class so that you can state its meaning to whatever degree of formality you like.

In the UML, there are several kinds of classifiers and classes; it's important that you choose the one that best models your abstraction of the real world.