N-Tier Classes These classes are used to separate the different tiers of a solution. These tiers are: the Business Tier used to validate the presentation tier objects and to wrap all other data access methods. Business-Logic Layer This class is the middle layer of an application. It encapsulates business rules and decouples business logic from presentation details. It is in charge of talking to the Data-Access Layer. ptii-061 Data-Access Layer This class is an application layer that sits between the Business-Logic Layer and the database. It deals with the complexity of reading and writing data to the database and decouples the business logic layer from the database details. ptii-062 Interoperability Layer This class encapsulates the details of your table and its data elements. The object is used to pass parameters from one layer to another of a layered distributed web application. ptii-063