Wednesday, January 31, 2007

ESB Primer

The Enterprise Service Bus (ESB) can be considered a virtual layer composed of a set of services that acts as a broker for “facilitating” SOA integration across all the IT systems and components that can or may possibly exists in an enterprise environment. ESB is a relatively new term emerging in the industry. Yet some of the rudimentary principles on which ESB is based on are relatively old (as in matured). The core objective of ESB is to enable agent based mediation between two service end points to accommodate service integration. To achieve such agent mediated service integration, the ESB uses web service and other integration technologies available. An ESB is not a pure play Web services solution. An ESB repertoire can include all the Web service standards, integration adapters, spectrum of business connectors, enterprise plug-ins to legacy platforms, messaging agents and brokers, process and workflow plug-ins, and message/data transformers. ESB acts as a ubiquitous process integrator to achieve the business service to IT service mapping.

The main objective of an ESB is to facilitate interactions across people, process, application and data. Apart from the integration enablers, ESB is also made up of components that provide intelligence for service integration such as interface transformation, service matching, QoS (transactions, security, addressing, messaging), service level monitoring and system monitoring. Apart from the stated pervasive services endowed by ESB, some of the prevalent service enablement that is possible through ESB are Composite Application Frameworks (CAF) and Business Process Choreography/Orchestration to achieve Business Process Integration (BPI).

CAF is an “execution shell” around applications supporting different business needs to provision an aggregate requirement by sharing the process of all these different applications. For example to achieve a quote-to-cash customer order management, an ERP will typically be integrated to a CRM system. This can be done using either the conventional integration strategies (direct integration) or through CAF. In the conventional itegration strategy, retiring any one of the integrated modules to bring in a newer module will break the overall composite environment. But in CAF execution shell, modules can be plug and played to an extent with comparatively minimal impact than the traditional methods. SeeBeyond’s ICAN suite, WebMethod’s CAF and SAP’s NetWeaver are some good CAF products available. The CAF may internally use a Business Process Choreography framework to enable flexible process orchestration across applications (ERP and CRM from the example) to enable adaptability across changing process components to support the business need (quote-to-cash from example). IBM’s Websphere Business Integration Server is an excellent business process orchestration and execution product available. The Websphere Business Integration Server uses a BPEL engine to achieve process choreography. The SOA and ESB are key enabling technologies for CAF and BPI.

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