UML(Unified Modeling Language)统一建模语言，是一种面向对象建模语言，它的主要作用是帮助用户对软件系统进行面向对象的描述和建模（建模是通过将用户的业务需求映射为代码，保证代码满足这些需求-Unified Modeling Language, UML (Unified Modeling Language) is an object-oriented modeling language, its main role is to help users of the software system descr iption and modeling of object-oriented (modeling by the user' s business needs mapping code, to ensure that the code to meet those needs