大多数文章中都或多或少的讲到了三层架构。表示层，业务层，数据层。又把业务层再细分，分为外观服务层，主业务服务，及数据库库服务层。

今天主要讨论一下业务层吧。举个最简单的例子。客户端获取数据。

-Most articles are more or less talking about the three-tier structure. Presentation layer, business layer, data layer. Business layer again subdivided into the appearance of service layer, the main business services, library services and database layer. Today, the main bar to talk about the business layer. Take the simplest example. Client access to data.