Is cloud computing possible without SOA?
Yes, but don't expect things to move very smoothly.
Is SOA possible without cloud computing?
Of course. But don't expect any impetus toward the loose coupling model you're trying to promote.
I just listened to a podcast with Mike Kavis, CTO of M-Dot, who sat down with my colleague at ebizQ, Peter Schooff, to talk about SOA and the cloud and the advantages and difficulties enterprises face moving from SOA to the cloud.
Practicing SOA gives many companies a leg up when they start looking at cloud formations, Mike observes. First, he says, there's the loosely coupled aspect of SOA -- very important. "Companies who aren't practicing service oriented architecture will be tightly coupled to their databases, will be tightly coupled to their infrastructure. So it's very hard for them to move, or shift, or change things around," he says. "Whereas companies with a service oriented architecture can look at their entire offering and say, 'hey, these pieces make sense to move the cloud, these other pieces don't,' and they can make those moves. Without a service oriented architecture, it almost becomes an all or nothing proposition and that's not a recipe for success."
Mike establishes, then, that SOA is a big enabler for cloud computing. But at the same time, cloud computing is a big enabler for SOA. As Mike put it in the interview: "We all know that SOA has had its troubles catching on, and I think the movement to the cloud is one of the best things that could happen to SOA. Because what you'll find is its very hard to move to the cloud when you're tightly coupled to your architecture. And then I also see a lot more requirements for businesses to integrate with partners, to leverage mashups, to do those types of things, connect into other Software-as-a-Service providers."
Mike did a great job of exploring the technical justification for SOA and cloud working together. Let me add there's an enormous business justification for the SOA-cloud alliance as well. For years, IT has been fighting the tides trying to get business to understand what SOA is about, why it should be funded, and what the results will be. But business quickly gets cloud computing. The best way to sell SOA to the business is as an internal cloud program. Cloud finally makes SOA tangible to the business.