Business Events
Analysis
Integration Models
Frameworks
Bizevex

There are two basic models for application integration. Each of these models provides specific benefits, depending on how the applications in question are to interact.

Message-Based Integration

Loosely-coupled applications interact asynchronously, using store-and-forward techniques in a messaging model. The connection between applications may be a direct (point-to-point) one, or an intervening application object, called a message broker, may manage it. Applications that share only information and do not otherwise need to run in concert are candidates for message-based integration.

• Where a single application communicates with a number of others with which it shares common semantics (or easily variable semantics through XML or other metaformat), a point-to-point connection provides the simplest integration and requires the least overhead and maintenance.
• Where multiple applications communicate among one another, a[n event-driven] broker object controls the message flow and performs any necessary message transformation and routing, based on standing rules and/or the message content.

In either case, other middleware products, platform-independent tools and services that carry out the generic functions of the broker may enhance interapplication connection.

Transaction-Based Integration

Tightly-coupled applications interact synchronously, in a transactional (ACID) model, requiring specialized programs to manage the interfaces: COM objects in the Microsoft environment or Enterprise Java Beans (EJB) on any platform running Java 2 Enterprise Edition (J2EE).

EJBs or COM objects are independent components that serve to bind applications. They act as wrappers around business processes or entities that must run simultaneously, invoke one another or otherwise share services in real time. (Example of a reservation system). The two platforms, MS and Java, have generally analogous integration models for invoking procedures or methods, addressing directories, accessing databases, and generating Web pages.

Comparison

The overhead and maintenance required for tightly-coupled applications is greater than that of loosely-coupled ones. Because tightly-bound applications are so interdependent, a change in any one application's interfaces necessarily requires modification to those of the others.

The development requirements of tightly- and loosely bound applications are more equivalent. That is because, in either case, a large portion of development effort must be devoted to analysis of each component application, and to the creation of the interfaces required by brokers, beans or other apps.