We were recently Tweeted an inquiry about what exactly cloud computing means.  If you are listening in to tech chatter these days it's impossible to avoid the flurry of opinions about what the cloud is.

So ... we figured we might as well add our two cents and spent a thought provoking morning developing a cloud stack analogy.

Cloud services tend to fit into the category of SaaS (Software-as-a-Service), PaaS (Platform-as-a-Service) or IaaS(Infrastructure-as-a-Service), each one delivering a service that encompasses the stack components below.  So, IaaS provides everything needed for server operation so that customers don't have to set-up their own server operation, hardware and server connectivity.  PaaS adds a further layer of integrating providing the traditional server stack elements and installed code bases and databases as well as frequently layering on a codeless development environment.  And SaaS delivers a complete application to end users via the browser with the rest of the cloud stack supporting it.

While this model seems very helpful in describing the rough layers of the cloud stack, there are is in fact a continuum of cloud services spanning from Iaas to Saas.  The key to understanding this continuum is to understand the trade-off between efficiency and flexibility of different requirements.  For example, I recently had a need for a collaborative mark-up tool that would quickly screen capture a website and allow me to add comments and graphics as a way to model user experience for our client projects.

I naturally turned to the cloud to seek solutions. Taking the IaaS route could have yielded something along the lines deploying an Amazon EC2 (aws.amazon.com) server and running Gimp as a cloud service ... a pretty cool idea for an enterprise solution but likely a 6 month endeavor and overkill for my simple requirement.  On the other hand I spent about 30 minutes searching the web and found the SaaS image tool Aviary (www.aviary.com) which did the job just fine.

This cloud continuum is also helpful to understand why we see PaaS as an optimal tool for business process application development.  Most SaaS applications are too limited in scope and lack the flexibility to support and enterprise or even small business management application.  On the other hand just leveraging IaaS for application hosting does not yield the efficiency and cost benefits that SaaS delivers.  PaaS tools like QuickBase (www.quickbase.com), WorkXpress (www.workxpress.com) and Wolf Frameworks (www.wolfframeworks.com) allow for flexibility and customization of applications at rapid speeds and low costs.

CLOUD CONTINUUM