Creating truly decoupled composite SOA applications requires a complete separation of the service consumer and the service provider.This is typically achieved through the use of asynchronous messaging.In an asynchronous messaging pattern, applications can perform in a”fire and forget” mode. This removes the need of an application to know details of the application on the other side. Additionally, it also improves resource utilization as applications are not holding onto resources until the interaction is complete. On the other hand, this introduces complexities of creating and managing message queues and topics. It requires that both the publisher of the message and the consumer use the same messaging technology. Each messaging system also has its own constraints on the types of programming languages and environments that can use the service.

In a service-oriented world, this tight coupling to the implementation of the underlying messaging system is at odds with the fundamental requirement of implementation independence. What’s needed is a level of abstraction that allows applications to generate an event using business terms and associate a business object in an implementation‑independent form.

Oracle SOA Suite 11g addresses this with the introduction of anew feature in the form of the Event Delivery Network.

Introducing events

The Event Delivery Network (EDN) in Oracle SOA Suite 11g provides a declarative way to use a publish/subscribe model to generate and consume business events without worrying about the underlying message infrastructure.

Developers only need to produce or consume events without having to deal with any particular messaging API like JMS, AQ, and MQ, and so on. Consuming an event means expressing an interest in the occurrence of a specific situation,while producing an event means advertising this occurrence.

Using the same concepts that are used in Web Service Definition Language (WSDL), EDN uses an XML-based Event Definition Language, which allows you to define the event and its associated,strongly typed data. This definition is then registered with the SOA Infrastructure and is available to all composites to publish or subscribe.