定位:怎么使用UML？

"黑夜给了我黑色的眼睛，我却用它寻找光明."同样一件东西怎么用确是不一定的，对于UML怎么使用也要有一个定位。Martin Fowler先生给出了三种使用使用UML的方式：蓝图blueprints ，骨架 sketches，编程语言。

三种使用方式比较容易区分出来的是：作为编程语言使用.ExecutedUML对工具的要求是非常高的-需要处理代码和图的同步问题等等.这里不做展开讨论，大家可以到国家文献中心找到更多相关资料：

源文档 <http://s.wanfangdata.com.cn/paper.aspx?q=executed%20UML&n=10&f=top> UML作为编程语言,典型应用时MDA.UML是MDA的事实标准，占领了90%的市场份额.“MDA 的愿景是定义一种描述和创建系统的新的途径。MDA 使得UML 的用途走得更远，而不仅仅是美丽的图画。很多专家预言MDA 有可能会带领我们进入软件开发的另一个黄金时代"。

Model-driven architecture (MDA) is a software design approach for the development of software systems. It provides a set of guidelines for the structuring of specifications, which are expressed as models. Model-driven architecture is a kind of domain engineering, and supports model-driven engineering of software systems. It was launched by the Object Management Group (OMG) in 2001.

源文档 <http://en.wikipedia.org/wiki/Model-driven_architecture>

Executable UML,often abbreviated to xtUML or xUML , is the evolution of the Shlaer-Mellor method[3] to UML. Executable UML graphically specifies a system using a profile of the UML. The models are testable, and can be compiled into a less abstract programming language to target a specific implementation.Executable UML supports MDA through specification of platform-independent models, and the compilation of the platform-independent models into platform-specific models. 

源文档 <http://en.wikipedia.org/wiki/Executable_UML>

难以区分的是蓝图blueprints 和骨架 sketches,从中文说文解字的角度我们无法获得一个满意的答案.按照Martin Fowler先生的论述我将二者的区别通过表格的形式列了出来，通过比较还是能看出各中端倪的：

Mode	Essence	Forward engineering	Reverse engineering	Tools	Practice
Sketch	selectivity	communicate ideas and alternatives	explain how some part of a system works	lightweight drawing tools	To help communicate some aspects of a system. Do it quickly and collaboratively, so a common medium is a whiteboard.
Blueprint	completeness	detailed design for a programmer to code up	convey detailed information about the code	CASE Tools (much more sophisticated )	Reducing programming to a simple and fairly mechanical activity

从上面的比较中可以看出sketches勾勒重点，蓝图blueprints注重完整性，无微不至.前者是一种探索性的explorative，后者是定义性的definitive。对于后者，一旦蓝图确定，编码工作基本上就没有什么创造性了.

出处：回头再说
责任编辑：bluehearts

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