As if cloud computing weren't a hard enough concept to grasp, there are gradations emerging that make the concept even more complicated. Relax. It's a natural evolution, as the capabilities behind the cloud concept become more explicit. What's important is to realize the potential and start planning for it.

Public cloud computing offerings are those you with which you are most likely already familiar. Applications delivered over the Internet in the software-as-a-service model, and computing resources such as storage or compute cycles delivered in the infrastructure-as-a-service model, are the most common forms of public cloud computing.

A private cloud, also known as a corporate cloud, uses cloud-like infrastructure and technology, such as virtualized servers in a scalable architecture, to run applications behind the corporate firewall.

A hybrid model takes advantages of both of these types of structures. An organization may choose, for example, to run its e-mail system in the public cloud while keeping highly sensitive, customer-oriented applications behind the firewall.

What model you choose may depend on several factors: size of organization, IT resources, time to market (speed of implementation), security requirements. For instance, SaaS in the public cloud provides organizations with limited resources a way to implement a needed application quickly and with low upfront costs. A private cloud, on the other hand, requires significant initial investment but offers behind-the-firewall security assurance.

Organizations of all sizes make use of infrastructure-as-a-service resources to boost capacity or support new systems. But are they making the best use of cloud computing's potential? Not according to Doug Hauger, general manager of Microsoft's cloud infrastructure group, as quoted in a recent InformationWeek article. "If you've got a hairball in your data center, and you move that hairball to an infrastructure-as-a-service, and you don't rework it, it's still just a hairball," Hauger said.

Which brings us to another important point: writing applications optimized for the cloud computing architecture. That's where platform-as-a-service comes in. Oh, I didn't mention that there's another form of cloud computing coming to the fore? Relax. The more the merrier, right?As if cloud computing weren't a hard enough concept to grasp, there are gradations emerging that make the concept even more complicated. Relax. It's a natural evolution, as the capabilities behind the cloud concept become more explicit. What's important is to realize the potential and start planning for it.