This dualism leads to some confusion as marketers increasingly talk about SOA products in terms of SaaS capabilities. A recent survey of CIOs and CTOs by the Object Management Group's (OMG) SOA Consortium indicated that there is an expectation that SOA has transformed the vendor marketplace so that significant software can be supplied via SaaS using an SOA approach.

But it is important to have clear definitions, said Bradley F. Shimmin, principal analyst of application infrastructure for Current Analysis LLC.

"I really consider SaaS as a delivery mechanism that supports single instance/multi- tenant applications," he said. "And I consider SOA as a philosophical framework for developing loosely coupled software. So, SOA is all about how software is structured and SaaS is all about how software is used."