Distinguishing between Software Oriented Architecture and Software as a Service: What's in a Name?

V arious IT professionals have, at one time or another, erroneously used the terms software as a service (SaaS) and service-oriented architecture (SOA) interchangeably. At best, this faulty practice creates confusion; at its worst, it can lead to poor designs. Our goal, therefore, is to clarify the meaning of these two often used and abused terms. Briefly stated, the difference between SaaS and SOA is that the former is a software-delivery model whereas the latter is a software-construction model. A better way to illuminate the differences between these two concepts is to use the well-known Zachman architectural model.1 In this article, we briefly examine the concepts of SaaS and SOA, followed by a brief history of software architectural models. We use the Zachman model to differentiate the two architectural approaches to building software. Because the Zachman model is so intuitive, the approach we take to describe the differences between SaaS and SOA works well even with non-IT professionals.