Defining a Cloud Reference Model

The cloud landscape is confusing -- with over 85 "cloud" vendors and various definitions of offerings it is difficult to evaluate services. The Cloud Reference Model brings order to this cloud landscape. The Model divides cloud-based application architecture into seven layers: Application, Transformation, Control, Instantiation, Appliance, Virtual, and Physical. Each layer focuses IT functionality on supporting a specific area of concern and abstracts details of other layers. Then application architecture design becomes an exercise in determining the necessary functionality at each layer -- assessing attributes like performance, security, and reliability is decoupled. Leveraging this approach we examine the "green-ness" of cloud-based architectures for which we assess the carbon footprint of Microsoft\´s Software-as-a-Service offerings.