Chapter 3 Design Figure 3-17. Business layer to data access layer Data Layer The data access layer is responsible for simplified access to data stored in databases, as shown in Figure 3-17. This layer contains a DTO, which is a mapping to the table; every column in the table is a member of the DTO. The DAO (data access object) helps you to create, delete, modify, or search for an entity using a simple object. The DAO design pattern is used to implement the data persistence layer. It is based on abstraction and encapsulation design, as it protects other parts of the application from any change in the data layer, for example, change of database from MySQL 86