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Analysis: SOA-Aware Network Infrastructure: Page 4 of 14

XML transformation deals with higher-level data formats at the messaging layer and above (see "Stacking up the Standards" in the gallery ). Apps designed for maximum interoperability tend to wrap messages in SOAP (Simple Object Access Protocol), while Web services on the Internet generally use other XML formats, collectively known as REST (Representational State Transfer.) Most ESBs support both of these, but not JSON (JavaScript Object Notation), a simple, non-XML format that has become wildly popular in RIAs (Rich Internet Applications).

Of the many WS-* standards that run over SOAP, the most important are WS-Security, WS-Addressing and WS-Interoperability. WS-Security lets Web services include encrypted data or digital signatures. WS-Addressing handles routing information, and WS-Interoperability is a set of profiles that describe how the WS-* standards can be used together. They're all XML-based, so it's relatively easy for an ESB to support any of them, as well as any custom data formats used by a service.

Because building a SOA is such a major undertaking, early ESBs were used only by very large enterprises. The total installed base in 2006 was less than 600, according to Gartner Dataquest, many in extremely large data centers: ESB pioneer Sonic Software, now owned by Progress Software, says that at least 20 of its customers run its Progress Sonic ESB on 100 or more CPUs. However, many more vendors are entering the game, and prices are falling as SOA adoption becomes more widespread. The latter trend will be aided in particular by the open-source ESB offerings of Iona and Red Hat's JBoss division; in May these companies acquired LogicBlaze and MetaMatrix, respectively, to boost their service-enablement features.

The ESB is rapidly becoming a standard part of every application platform. The EAI (Enterprise Application Integration) players that shipped the first ESBs have been joined by BEA Systems, IBM, Oracle, SAP and Sun Microsystems, all promising an easy way to build and orchestrate services. Even Microsoft now describes its BizTalk Server as an ESB, having previously promoted its products as "something better," while Avaya says it has an ESB focused on telephony applications.

Integration between an ESB and an application platform makes sense from a service-enablement standpoint: If most of your applications are built on BEA's AquaLogic or IBM's WebSphere, there's no reason not to use the same product for an ESB. Those needing to mash up legacy applications running on different platforms may be better off with a specialist, such as Cape Clear Software, Fiorano Software or Progress Software's Sonic.