J2EE BluePrints 3.2 Overview of Client Options Choices such as which tier or tiers of the application that clients interact with, the protocols used for this communication, and the implementation language used for the client are dependent on several factors.
Different tiers expose different levels of detail and complexity.
The Web tier presents a simplified functional facade to the application. It takes care of presentation issues for the client. The EJB tier presents an interface to access and manipulate the business objects according to the business rules set in the application, leaving presentation issues to the client connecting to it. The enterprise information system tier presents a raw view of the data, delegating the responsibility of enforcing the business rules, as well as presenting the data to the client. The protocols used for communication have different strengths and limitations.