Patrick Leonard, VP of Product Development takes a crack at ESB on the Webservices.org web site.
While suggesting that the association between Enterprise Service Bus (ESB) and SOA has good reasons, including guaranteed message delivery and back end integration capabilities, he suggests that Service Orientation is not the same as Bus Orientation. The piece goes on to say:
Observers of Service Component Architecture also suggest that while SCA (and its little brother Service Data Objects, or SDO) provides for a useful language-independent description language for service architecture tooling, it is focused on service assembly, which is only one (very significant) part of the requirement set of SOA.
While suggesting that the association between Enterprise Service Bus (ESB) and SOA has good reasons, including guaranteed message delivery and back end integration capabilities, he suggests that Service Orientation is not the same as Bus Orientation. The piece goes on to say:
Reports of the ESB’s decline have been exaggerated, but its role will be redefined. An ESB can be a great way to deliver messages reliably from point A to B (among other things), but it isn’t best suited to serve as the cornerstone of an SOA implementation – there are enterprise-ready alternatives that are designed specifically for SOA that enable greater realization of the true goal of implementing an SOA.
The Service Component Architecture (SCA) ( www.osoa.org) and Microsoft’s WCF are both good examples of reference architecture for an SOA. There is now product available from multiple vendors, with both commercial and open source options available for SCA.
The Service Component Architecture and WCF are both attempts to provide a language-neutral programming model that meets the needs of enterprise developers who are developing software that exploits Service Oriented Architecture characteristics and benefits. SCA is not intended to be a "Reference Architecture" as such, however, it does appear to be a helpful specification for tools vendors. Of note is that ESB, SCA and WCF are all TLAs (Three Letter Acronyms) but they are not standards.Observers of Service Component Architecture also suggest that while SCA (and its little brother Service Data Objects, or SDO) provides for a useful language-independent description language for service architecture tooling, it is focused on service assembly, which is only one (very significant) part of the requirement set of SOA.