Lori MacVittie recently channeled Gartner's Daryl "G-Man" Plummer in an analysis of the converging roles of SOA and cloud computing.
Essentially, the challenge with cloud computing comes along when you want to move workloads in and out of the cloud, versus entire applications. And Lori and Daryl are very careful to emphasize the point that many enterprises may not want entire applications moved into the cloud. Pieces are fine. The preferred approach for many organizations seeking the most robust and cost-effective solutions may be hybrid arrangements of clouds and on-premise data centers.
Lori defines a "workload" as a "discrete block of application logic that is self-contained, and can be executed on its own" -- such as a function, method, or Web service. The problem the cloud has it that it was never designed to assist in decomposition of monolithic applications into composite processes -- "it was designed, for the most part, to run applications," she says.
So here's the challenge and here's where SOA comes into the picture:
"In order to move a “workload” into the cloud you have to decouple it from the application; you have to use the basic principles associated with SOA and decompose the application into its composite processes such that you can distribute those processes in a way that most effectively utilizes the processing power at hand – whether that’s locally or in the cloud. You can’t simply move a monolithic application into the cloud and expect the cloud provider to be able to dig into it and optimize the execution of specific processes. It just isn’t that smart."
The whole point of SOA, Lori reminds us, is to decompose applications into discrete services so they can be distributed intelligently. "If one service is reused by multiple business processes it can be replicated or moved into the cloud so that it scales appropriately to meet the demands that are placed upon it by other applications."
SOA was conceived and designed to enable the deployment and consumption of services anywhere, anytime, inside or outside the firewall. Sounds pretty cloudish to me.