For nearly ten years, the Unified Modeling Language(UML) has been the industry standard for visualizing, specifying, constructing, and documenting the artifacts of a software-intensive system. As the de facto standard modeling language, the UML facilitates communication and reduces confusion among project stakeholders. The recent standardization of UML 2.0 has further extended the language's scope and viability. Its inherent expressiveness allows users to model everything from enterprise information systems and distributed Web-based applications to real-time embedded systems.
The UML is not limited to modeling software. In fact, it is expressive enough to model non-software systems, such as workflow in the legal system, the structure and behavior of a patient healthcare 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 requires learning three major elements: the UML's basic building blocks, the rules that dictate how those building blocks may be put together, and some common mechanisms that apply throughout the UML.
近十年来，统一建模语言（UML）已经成为工业标准，它可用来可视化、规范化说明、构建以及文档化软件密集系统中的开发制品。作为事实上的工业标准，UML能够方便项目相关人员的沟通并减少理解上的二义问题。UML 2.0标准扩宽了该语言的应用范围，它所具有的表达能力能够让用户对企业信息系统、分布式Web系统和嵌入式实时系统进行建模。
UML不仅能够对软件系统进行建模，实际上，它具有足够的能力去对法律系统中的工作流、病人监护系统中的结构和行为、飞行战斗系统和硬件系统进行建模。
为了理解UML，需要具备该语言的概念模型，这需要学习三个主要元素：UML的基本构造块，基本构造块的关系规则和应用这些构造块与规则的通用机制。