What is the SOA?
SOA is an architectural style whose goal is to achieve loose coupling among interacting software agents. A service is a unit of work done by a service provider to achieve desired end results for a service consumer. Both provider and consumer are roles played by software agents on behalf of their owners.
- 面向服务架构是一种能实现软件组件的低耦合的一种架构风格。
- 低耦合：组件化设计软件来提高软件组件的复用率（减少重复开发，提高效率），可管理性。
- 服务是指物理资源的逻辑展现。比如说，开发天气Web APP，开发者（消费者）并不需要去关心如何去测量天气数据，只要通过前端技术去展示从服务开发商（提供者）请求来的天气数据就行。
- 服务的形式可以是各种各样的，服务的开发是面向信息接口的；像轻量化的服务有Json和XML格式的数据。
- 服务的消费者和提供者，这两种角色不是固定的。消费者利用提供者服务开发出来的应用也可作为服务提供给其他消费者。并且服务的开发具有独立性。
- SOA具体的实现有RESTful设计原则：利用HTTP协议的各种请求方法来实现网络应用。
This sounds a bit too abstract, but SOA is actually everywhere. Let 's look at an example of SOA which is likely to be found in your living room. Take a CD for instance. If you want to play it, you put your CD into a CD player and the player plays it for you. The CD player offers a CD playing service. Which is nice because you can replace one CD player with another. You can play the same CD on a portable player or on your expensive stereo. They both offer the same CD playing service, but the quality of service is different.
References
Data-intensive Systems Slides of University of St Andrews
