However, while the DAL cleanly separates the data access details from the presentation layer, it does not enforce any business rules that may apply.
不过，即使DAL将数据访问的细节从表示层中分离出来了，可它却不能处理任何的业务规则。
This layer also handles the requests from the Presentation layer and interacts with the DAL to retrieve the data from the back end and request the DAL to perform data persistence.
这个层还处理来自表示层的请求，并与DAL交互以便从后端检索数据并请求DAL执行数据持久性。
Data is retrieved from the location Data Provider — a Data Abstract Layer (DAL) component — which caches all locations in memory.
从位置数据提供者检索数据，这是一个数据抽象层(DAL)组件，在内存中缓存所有位置。
The example in this article consists of the Data Abstract Layer (DAL), Data Transfer Objects (DTOs), the Business Logic Layer (BLL), the Presentation Layer, and supporting helper classes.
本文中的示例包含数据抽象层（DAL）、数据传输对象（DTO）、业务逻辑层（BLL）、表示层和用于支持的helper类。
The example in this article consists of the Data Abstract Layer (DAL), Data Transfer Objects (DTOs), the Business Logic Layer (BLL), the Presentation Layer, and supporting helper classes.
本文中的示例包含数据抽象层（DAL）、数据传输对象（DTO）、业务逻辑层（BLL）、表示层和用于支持的helper类。
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