593/2000 The three-tier pattern is

593/2000 The three-tier pattern is based on the two-tier pattern, which adds a new level to it. This pattern logically divides application functions into three layers: the customer display layer and the business logic layer, and the data layer. The customer display layer is the graphical interface on the application service for the customer, which is helpful for the user to understand and locate the application efficiently. The business logic layer between the display layer and the data layer provides a clear level to implement the business logic of the enterprise, which encapsulates the application model associated with the system, and separate the user presentation layer from the database code. This layer provides the linkage between the client application and the data service, the main function is to execute the application policy and encapsulate the application pattern, and present the encapsulated pattern to the client application. The data layer is the lowest of the three-tier Schemas used to define, maintain, access, and update data and to manage and satisfy application services’requests for data.