Figure 5

Design of a system within an application server typically involves three layers: an infrastructure layer which stores the data; a domain layer which is populated with vertical object models; and an application layer which models how an application can interact with the domain objects. The application server provides both resource management and service based functionality for each of these layers. In EJB terms there is: the infrastructure layer corresponding to a database, typically with O-R mappings through hibernate; the domain layer corresponding to entity beans, which basically function as an object cache; and the application layer corresponding to sessions beans or Web Services (with stateless session bean mappings).