A pattern for modern computing

Software as a Service (SaaS) has become a popular term within software industry circles since its introduction in early 1999. While many in the press have predicted that SaaS may eventually replace the incumbent model for software delivery, more likely an approach will evolve that combines the best of both worlds. This paper examines the core pattern of SaaS in pragmatic terms. It also outlines some of the strategic advantages SaaS can provide over distributed and shrink-wrapped software. This paper is not intended to be a singular authoritative source for defining SaaS; indeed it would not make sense to try to create such a document.

The original concept of SaaS, based on the Application Service Provider model, began to circulate in the technical community around 1999. (An ASP is a company that offers access to software and/or network applications, typically via the Internet.) The first written paper that included all the core elements of SaaS is generally thought to be a paper presented at the Seventh Asia-Pacific Software Engineering Conference (APSEC 2000), written by Keith Bennett, David Budgen, Pearl Brereton, Paul Layzell, Linda Macaulay, and Malcolm Munro of various institutions within the UK. The paper, titled Service-Based Software: The Future for Flexible Software, turned out to be a rather prophetical look at the evolution within the software industry that was enabled by a global network and portable data. It is important to note that the advent of the eXtensible Markup Language (XML), combined with a globally accessible network, has resulted in new ways to deliver software functionality to end users. (The eXtensible Markup Language is a W3C Recommendation.) When people began to recognize that this model for delivering software functionality offered large advantages over conventional software delivery, it began to rapidly attract large numbers of supporters.

To fully understand the advantages offered by SaaS, it is essential to understand the underlying patterns, technologies, and lexicon at work. This paper is written as an advanced primer to explore the various aspects of SaaS, capture the base pattern, and outline its main advantages.