wiki定义: UML is a general-purpose, developmental, modeling language in the field of software engineering, that is intended to provide a standard way to visualize the design of a system.

目的： UML was originally motivated by the desire to standardize the disparate notational systems and approcaches to software design.

成就: In 1997, UML was adopted as a standard by the Object Management Group(OMG), and has been managed by this organization ever since. In 2005, UML was also published by the International Organization for Standardiation (ISO) as an approved ISO standard. 不过UML主要是用在教育和学术界，在业界已渐渐不太使用。

作用：UML offers a way to visualize a system's architectural blueprints in a diagram, including elements such as:

1. Any activities (jobs)

2. Individual components of the system, and how they can interact with other software components.

3. How the system will run.

4. How entities interact with others(components and interfaces)

5. External user interface.