dnn架构之provider model研究---DNN3.0

     provider model这个层是介于数据访问层和数据存储层中的一个层。原文：It also provides a new level of abstraction between the data access layer and the data store。
     provider model主要在下面几个方面使用：
❑ Data Provider
❑ Scheduling Provider
❑ Logging Provider
❑ HTML Editor Provider
❑ Search Provider
❑ Friendly URL Provider 
      主要结构图如下所示：

  这个层的主要设计思想:
      Build things so they do not depend on the details of other things.
     A provider is a contract between an API and the business logic that establishes the functionality that the implementation of the API must provide