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introduction


This whitepaper introduces the Unified Modeling Language (UML), version 1.1. It reviews the diagrams that comprise UML, and offers a Use-Case-driven approach on how these diagrams are used to model systems. The paper also discusses UML's built-in extensibility mechanisms, which enable its notation and semantics to be extended. This paper also suggests extending UML by two non-built-in techniques: CRC cards for responsibility-driven analysis and entity relation diagrams for modeling of relational databases.



What Is UML?
The Unified Modeling Language prescribes a standard set of diagrams and notations for modeling objectoriented systems, and describes the underlying semantics of what these diagrams and symbols mean. Whereas there has been to this point many notations and methods used for object-oriented design, now there is a single notation for modelers to learn.
UML can be used to model different kinds of systems: software systems, hardware systems, and real-world organizations. UML offers nine diagrams in which to model systems:



UML Provides Standard Notation and Semantics
UML prescribes a standard notation and underlying semantics for modeling an object-oriented system. Previously, an object-oriented design might have been modeled with any one of a half dozen popular methodologies, causing reviewers to have to learn the notational semantics of the methodology before trying to understand the design. Now with UML, different designers modeling different systems can readily understand each other’s designs.