For neady ten years，the Unified Modeling Language(UML)has been the industry standardfor visualizing，specifying，constructing，and documenting the【S1】of a software-intensivesystem．As the【S2】standard modeling language，the UML facilitates communication andreduces confusion among project【S3】．The recent standardization of UML 2．0 has furtherextended the language’s scope and viability．Its inherent expressiveness allows users to【S4】everything from enterprise information systems and distributed Web·-based applications to real-timeembedded systems．The UML is not limited to modeling software．In fact，it is expressive enough to model【S5】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 of hardware．To understand the UML，you need to form. a conceptual model of the language，and this re—quires learning three major elements：the UML's basic building blocks，the rules that dictate howthose building blocks may be put together，and some common mechanisms that apply throughout theUML．
【S1】
A．classes
B．components
C．sequences
D．artifacts
