J2EE for Enterprise Integration - Guide to Cloud Computing for Business and Technology Managers - page 139

enforceable policies or rules applicable to them. The latter include
the requirement for persistence of the state of the entities as reflected
in the snapshot of all attributes.
• Business processes carry out the tasks of the enterprise. They have
some kind of specified workflow and essentially involve one or more
business entities. They must be executed in a secure manner and
also be accessible via a host of user interfaces or devices or clients.
• User interactions carry out the access and display of information
related to business entities as an outcome of some business pro-
cesses for scrutiny by the users of the enterprise application. This
essentially involves some kind of screen flow or page navigation,
attributes for presentation, user requests, or generated responses,
that is, static or dynamic content, form-oriented processing, and
error handling. The user interaction could be via a host of user inter-
faces or devices or clients.
Each of these elements gives rise to the three primary architecture layers of
the reference architecture. These layers could reside on the same physical
layer or be distributed across a network. Figure 6.1 presents the three archi-
tecture layers constituting the reference architecture.
6.2.1.1 User Interaction Architecture
User interactions are modeled by user interface components that com-
prise the User Interaction Architecture. In J2EE platform, this is typically
implemented as a combination of servlets and Java Server Pages (JSP). In a
Web-based application, this layer would process HTML form submissions,
manage state within an application, generate Web-page content, and control
navigation between pages. Many of the functions within this layer can be
automated through configurable foundation components.
6.2.1.2 Service-Based Architecture
Business processes are modeled by service components that comprise the
Service-Based Architecture. In J2EE platform, this is typically implemented
as a process-oriented object wrapped with a stateless Session Bean. The con-
cept of services allows the front end to be decoupled from the back-end busi-
ness object components. The service-based layer adds tremendous value in
terms of flexibility, reusability, and component design.
6.2.1.3 Business Object Architecture
Business entities are modeled by object components that comprise the
Business Object Architecture. Each of these components manages the data