Just as SOA is not a specific product that you can buy, neither does it describe a specific approach that you should use. Recent research by the Aberdeen Group does find that a company's SOA strategy can often be linked to company size. The report, entitled, "Enterprise Service Bus and SOA Middleware," throws SOA customer needs into three different buckets: SOA Lite, SOA ERP, and Enterprise SOA.

The report starts with the premise that enterprise service bus (ESB), as messaging middleware, "provides the secure interoperability and message transport services between application services in a SOA environment." Because ESB provides the SOA "highway" infrastructure, Aberdeen theorized, "its adoption is a proxy for overall market adoption of SOA technology."

The report states that "SOA Lite is for users who are primarily deploying web services that do not require mission-critical capabilities such as high-volume scalability, high availability and failover, management, governance, and security." It says further that "SOA ERP is used by companies that are choosing to deploy SOA surrounding their ERP application software," and that "Enterprise SOA requires and uses mission-critical SOA middleware capabilities."

This last approach, Enterprise SOA, represents the leading edge of SOA. Although Enterprise SOA is closely associated with larger enterprises, the issues inherent with these customers resonate with all companies and departments that are either considering or implementing an SOA strategy.

The Aberdeen report notes that major technology challenges involved with Enterprise SOA include creating metadata repositories and registries, managing security and governance, and of course, the familiar RAS trio of reliability, availability, and scalability.

Although there are numerous high-profile business-to-consumer applications being developed today, Aberdeen believes that about two-thirds of the Enterprise SOA activity it surveyed is concentrated on business-to-business applications and scenarios.

The mood in enterprise IT is hardly conservative, as evidenced by the fact that a full 46% of respondents are planning to deliver more than three major application integration projects this year using SOA. Aberdeen characterizes this statistic at attesting to a "strong and rapid" adoption of SOA technology within IT organizations, one that "is not business as usual."

So what scale is truly being discussed here? According to this report, respondents will deploy between 3,700 and 5,500 servers for edge applications and between 2,700 and 4,500 at datacenters. "The implication is that servers running ESB - and the rest of the SOA software stack - are beginning to create demand for enterprise server hardware purchases," the report notes. "We believe SOA will drive significant hardware purchases since the SOA value equation essentially trades off computing inefficiency (e.g., XML) for higher labor productivity," the report also states.

In deploying on this scale, survey respondents said that buying evaluations are driven by ease of integration, and flexibility with current and planned applications; ESB business process control, change, management, government, and life-cycle capabilities; and the completeness of the ESB product's offering. A successful strategy often involves having enterprise architect teams extending successful departmental approaches across the enterprise.

There was a philosophical split among these buyers, the report found, with slightly less than half of organizations "planning to standardize on SOA software from a single vendor," and about the same percentage planning to "employ a best-of-breed strategy with ESB and other SOA software purchases, believing industry standards for SOA will minimize integration risks."

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