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ESBs are a very hot topic right now - one of the most popular topics on ebizQ. In fact, ESBs are being touted as an integral part of an SOA infrastructure. However, there is still some question as to exactly what an ESB is. Here are some examples I found on the Web.

From Webopedia: “Short for Enterprise Service Bus, also referred to as a message broker. ESB is an open standards-based distributed synchronous or asynchronous messaging middleware that provides secure interoperability between enterprise applications via XML, Web services interfaces and standardized rules-based routing of documents. http://isp.webopedia.com/TERM/E/ESB.html

This definition describes the functionality of an ESB. This definition essentially says the ESB is synonymous with the term message broker. It also says the ESB is standards-based. However, while most message brokers now support Web services, the underlying technology typically is not standards-based. The definition also defines an ESB as having a distributed architecture as opposed to a centralized hub-and-spoke architecture that many message brokers have. This is an active point of contention. Gartner, for example, does not think that architecture is part of what defines an ESB - but it has more to do with Web services. It is also interesting to note that the definition says the ESB provides standardized rules-based routing, although there are no current standards for rules-based routing – just the message formats and communication protocols. The routing engines and algorithms are generally proprietary.

The Computing Dictionary defines an ESB as “A message broker that supports Web services.”
(http://computing-dictionary.thefreedictionary.com/ESB). Short and to the point. This would mean that all message brokers (which at this point all support Web services) are also ESBs. In fact, many vendors are taking the approach of renaming and/or repositioning their brokers as ESBs.

Bitpipe defines an ESB as “An enterprise integration architecture that allows incremental integration driven by business requirements, not technology limitations.” (http://www.bitpipe.com/tlist/ESB.html).
This one makes me LOL. What does it even mean?

According to Brenda Michelson, Senior Vice President and Senior Consultant/Analyst at Patricia Seybold Group, “An ESB is an open standards, message-based, distributed, integration solution that provides routing, invocation, and mediation services to facilitate the interactions of disparate distributed information technology resources (applications, services, information, platforms) in a reliable manner.” You can check out Brenda’s two-part Enterprise Service Bus Q&A on ebizQ (http://www.ebizq.net/hot_topics/esb/features/6117.html?page=1).
This definition defines the ESB as a standards-based technology. Brenda does not equate message brokers with ESBs.

How would you define an ESB? Have you implemented, or are you currently implementing, or planning to implement an ESB in your company? Please share your experience for the benefit of the entire community.

Posted by bethgb at 05:35 PM in Industry Trends | Digg This | Add to del.icio.us