传统规范语言的劣势在于，它们是由拥有稳固数学知识的人员使用的，使用它来建模系统很困难。
The disadvantage of the traditional formal languages is that they are used by people who possess a solid mathematical knowledge, but they are difficult to use for a modeling system.
第二章，介绍了统一建模语言UML的基本概念与有关知识；
The second chapter introduces the essential conceptions and related knowledge of the UML.
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