Programming Layers

(http://www.docirs.cl/arquitectura_tres_capas.htm)

The layered programming is a programming style in which the primary objective is the separation of business logic from the logic design, a basic example of this is to separate the data layer from the presentation layer to the user.

DAL: A Data Access Layer is a layer of a computer program which provides simplified access to data stored in persistent storage of some kind, such as an entity-relational databse.

This data access layer is used in turn by other program modules to access and manipulate the data within the data store without having to deal with the complexities inherent in this access.

BL: Business logic is a non-technical term generally used to describe the functional algorithms that handle information exchange between a database and a user interface. It is distinguished from input/output data validation and product logic.

Presentation Layer: it is seen by the user (also called the "user layer"), introduced the system to the user, communicates to capture information and user information in a minimum of process (perform a filtering Prior to check for any formatting errors). This layer communicates only with the business layer. It is also known as graphical interface and must have the characteristic of being "friendly" (understandable and easy to use) for the user.