Lorraine Lawson recently posted an insightful commentary about the SOA-Software as a Service connection, drawing on observations by Robert Schneider.
Schneider pointed out that many SaaS vendors “get it” when it comes to SOA: "their offerings are much more SOA-friendly, and often comply with many of its best practice guidelines. Of course, there are some horrendous exceptions to the rule, but SOAP-based, WSDL-defined services have become the de-facto standard for integration with SaaS solutions."
By employing SOA in their solutions, SaaS vendors smooth the way for integration among their customers.
And the synergy works the other way as well. Namely, that SOA can be viewed as SaaS, delivered internally. SOA essentially is "Software as a Service" contained within the enterprise walls.
The analogy makes a great elevator speech, especially if one is hard-pressed to describe the philosophy of SOA to end-user customers, whose eyes tend to glaze over when they start hearing about WSDL and BPEL and loose coupling. But SaaS -- everyone gets that. You don't have to buy and install the program CDs, you just use what you need off the Internet, and are charged on a metered basis.
Does SOA not work in the same fashion when delivered across the enterprise and beyond?
Rather than building, maintaining, or delivering their own services, business units subscribe to SOA-based services from a publisher somewhere else in the enterprise, or even outside the enterprise. Someone else worries about upgrades, maintenance and testing; you consume the service, and pay on some pay-as-you use arrangement. Sounds a lot like Software as a Service.
Conversely, while SaaS providers themselves may not necessarily be using SOA, it's probably in their best interest to align their services using SOA methodologies and protocols.
Really disappointing. SaaS is not SOA. A remote application is not a SOA service.
The "service" in Software as a Service means providing a remote application as a product to the client.
A SOA service is lower level, and is accessed by applications or other SOA/SOAP services. It has no front ends, and is only talked to by SOAP following the OASIS and W3C guidelines.
SOA "services" and SaaS "service" are not even related.