is low-cost, easily configurable, intuitive, user-friendly, and open to any tools customers choose. Characteristics ¹ Some do not regard process choreography as an ESB function. For example, see M.Richards. ² While process choreography supports implementation of complex business processes that require coordination of multiple business services (usually using BPEL), service orchestration enables coordination of multiple implementation services (most suitably exposed as an aggregate service) to serve individual requests.'' These solutions often focus on low-level ESB functions, such as connectivity, routing and transformation, and require coding or scripting to implement orchestration. Developers operating at a project or tactical level, e.g., just trying to fix a problem, often gravitate toward lightweight service bus technologies, but there is often ongoing tension between these initiatives and an enterprise architecture whose goal it is to optimize infrastructure across multiple projects. If the message broker, the ESB software, translates a message from one format to another, then as with any translation, there is the issue of semantics of the message. For example, a record can be translated from JSON to XML, but the same set of fields can be interpreted differently by different applications, specifically in the case of the various corner cases that are usually known only to developers that have extensive experience with the application that is connected to the ESB. For the known corner cases the number of tests that cover all corner cases increases exponentially with every application that is connected to the ESB, because every ESB-connected application must be tested against every other application that is connected to the ESB. Key benefits Scales from point-solutions to enterprise-wide deployment (distributed bus) More configuration rather than integration coding No central rules-engine, no central broker Easy plug-in and plug-out and loosely coupling system Key disadvantages Slower communication speed, especially for those already compatible services Single point of failure, can bring down all communications in the Enterprise High configuration and maintenance complexity Products Notable products include: Proprietary Candle's Roma ESB - bought by IBM and became WebSphere ESB IBM App Connect, formerly IBM Integration Bus and IBM WebSphere ESB InterSystems Ensemble Information Builders iWay Service Manager Microsoft Azure Service Bus Microsoft BizTalk Server Mule ESB Oracle Enterprise Service Bus Progress Software Sonic ESB (acquired by Trilogy) SAP Process Integration TIBCO Software ActiveMatrix BusinessWorks webMethods enterprise service bus (acquired by Software AG) Sonic ESB from Aurea XIATech Single Data View Open-source software Apache Camel Apache ServiceMix