● For nearly ten years, the Unified Modeling Language (UML) has been the industrystandard for visualizing, specifying, constructing, and documenting the  （71）  of asoftware-intensive system. As the  （72）  standard modeling language, the UML facilitatescommunication and reduces confusion among project  （73） . The recent standardization ofUML 2.0 has further extended the language's scope and viability. Its inherent expressivenessallows users to  （74）  everything from enterprise information systems and distributedWeb-based applications to real-time embedded systems.    The UML is not limited to modeling software. In fact, it is expressive enough to model（75）  systems, such as workflow in the legal system, the structure and behavior of a patienthealthcare system, software engineering in aircraft combat systems, and the design ofhardware.    To understand the UML, you need to form a conceptual model of the language, and thisrequires learning three major elements: the UML's basic building blocks, the rules that dictatehow those building blocks may be put together, and some common mechanisms that applythroughout the UML.