任意的数据源(文件、Web服务、定制存储、应用逻辑层等)。

Any data source (file, web service, custom store, application logic layer, etc).

youdao

另外，被发送到远程数据源的查询由执行层根据缓存内容和高级空抑制逻辑进行进一步优化。

In addition the queries which are sent to remote data sources are further optimized by the execution layer based on cache content and advanced null suppression logic.

youdao

另外，系统功能上分成三个层次结构，即表示层、业务逻辑层和数据源层。

In addition, the whole system is divided into 3-tier in functionality, representation level, business logic level and data level respectively.

youdao