SaaS and SOA: Together Forever

As Frank Sinatra often crooned, "Love and marriage, love and marriage, go together like a horse and carriage." It's pretty much the same relationship between services-oriented architecture (SOA) and software as a service (SaaS), and as the song would have it, "you can't have one without the other."

From a SaaS delivery perspective, SOA is what separates the current generation of SaaS providers, epitomized by the likes of Salesforce.com and NetSuite.com, from the failed application service providers (ASPs) of the dot-com era. From a consumption perspective, you certainly don't require a SOA to use SaaS, but if you want to effectively mix and match external services with on-premise assets and services, SOA will make it possible to efficiently build, deploy and manage composite apps.

We explore the relationship between SaaS and SOA, two emerging approaches for delivering IT functionality, applications and end-to-end business processes. If you're thinking of using SaaS, look beyond the buzzwords and price points, and make sure there is the solid foundation of SOA; without it, there's little

chance that service will scale and flexibly change with your needs. And if you're building or considering SOA within your enterprise, keep in mind that SaaS offerings (and lower-level services) will be crucial ingredients that will help you quickly deliver composite applications without getting bogged down in development.

SAAS MINUS SOA EQUALS ASP

Like SOA, SaaS is one of those white-hot buzzwords getting what might seem to be an inordinate amount of attention. After all, SaaS accounted for only 5 percent of the business software market in 2005, according to Gartner. That growth has analysts, investors, CIOs and enterprise architects taking notice: by 2011, Gartner expects 25 percent of business software to be delivered SaaS style--a 500-percent increase.

Back when SaaS players were known as ASPs, they enjoyed a great deal of hype as well, but barriers to scalability, flexibility and, ultimately, profitability proved to be the undoing of many ASPs. "It boils down to whether you have a multitenant environment or not," says Philippe Vincent, a partner at Accenture who advises software vendors on the emerging SaaS market (see "Debriefing"). "The first-generation ASPs offered conventional software on demand in a single-tenant environment, and they didn't do too well. That's essentially outsourcing application management and maintenance and offering it on demand."

In contrast, SOA-enabled SaaS providers can serve thousands or even tens of thousands of customers out of the same instance of the application, and their architectures and best practices enable them to scale, flexibly change and version the software in a very efficient way (Salesforce.com, for example, boasts it has nearly 25,000 customers and more than 500,000 subscribers). Be warned, however, that many of the thousands of lesser-known vendors now hopping on the SaaS bandwagon aren't building on the foundation of SOA.

"SaaS vendors have to be able to offer something that is flexible enough to meet customer needs, but you can't do that efficiently without a very good SOA model," says Vincent. "If they don't have the flexibility to deliver the functionality you want, or if they can't integrate with you significantly faster than a classic on-premise piece of software could, odds are it's not real SaaS."