IBM E02HMLL-I Implementation Guide - Page 17

Publish-and-subscribe interactions Connectors and collaborations use a publish-and-subscribe interaction to move information about application events into the IBM WebSphere Business Integration Server Express for processing. In the publish-and-subscribe interaction, a collaboration begins its business process when it is triggered to do so by receipt of a business object for a particular type of triggering event-for example, Employee.Create-that represents an application operation. The name of the business object (Employee) indicates a type of business entity. The verb (Create) indicates an operation that occurred on that entity. Therefore, the Employee.Create event reports the creation of an employee entity. The publish-and-subscribe interaction enables a triggering event to reach a collaboration as follows: v A collaboration subscribes to the event that can trigger its execution. A collaboration subscribes to an event by requesting it, and then waiting for it. A collaboration that subscribes to Employee.Create starts executing when the business object for the Employee.Create event arrives. v An event occurs in an application, and the event is detected by the application connector's event notification mechanism. The connector supplies the event to one or more collaborations by publishing it-making it available as a business object. Depending on the connector, an event can be published to a collaboration either asynchronously or synchronously. In addition, if the long-lived business process feature of the collaboration is enabled, a collaboration can maintain the event in a waiting state, in anticipation of incoming events satisfying pre-defined matching criteria. Access requests A collaboration can be designed to be triggered by direct calls that are sent by an access client, received by the Server Access Interface, and sent to the collaboration as business objects. In an InterChange Server Express implementation, calls sent to collaborations through the Server Access Interface are referred to as access requests. Access requests can originate from external sources or from sources that are configured within the InterChange Server Express implementation. Access request interactions are useful when synchronous communication is important-as when, for example, a customer representative uses a web browser to request inventory status information over the Internet. Request/response interactions A collaboration begins processing data when it is triggered to do by receipt of a triggering business object. The triggering business object can be the result of either an access request or an event notification. Once a collaboration has been triggered, it can make requests of connectors to which it has been bound, and receive responses. The collaboration makes its requests-referred to as service call requests-in the form of generic business objects. The connectors transform the generic business objects into data entities that are understood by the specific application or data format for which the connector is designed. Chapter 1. Overview of IBM WebSphere Business Integration Server Express 5