Does Platform as a Service (PaaS) exhibit a distinct cloud architecture model?  What specific cloud reference architecture components are required?

The WSO2 vision of Cloud-aware applications and WSO2 Cloud Reference Architecture is found in a blog post here.  Read this blog post to review cloud architecture alternatives.

After reviewing architecture models from several vendors and industry organizations, I believe we are witnessing an early evolutionary period as we transition from web application architecture to cloud application architecture.  The analysis is based on reviewing the following vendor and analyst architecture diagrams:

• NIST Cloud Computing Reference Architecture [1,2]
• NIST Cloud Service Management [1,2]
• IBM Cloud Computing Reference Architecture [8,9]
• IBM Common Cloud Management Platform [8,9]
• WSO2 Cloud Reference Architecture [0]
• Oracle Reference Architecture [3]
• Oracle Basic Platform as a Service Cloud Architecture [4]
• Sonata SaaS Enablement Services [16]
• JBoss in Cloud [5]
• RedHat OpenShift Flex Architecture [6]
• CloudFoundry Architecture [10]
• CloudBees PaaS Reference Architecture [11]
• HP CloudSystem Architecture [7]
• Progress OpenEdge SaaS Service Architecture [12]
• Intel SaaS Conceptual Architecture [13,14]
• Apprenda SaaSGrid Architecture [15]
• Amazon Web Services [17]
• Microsoft Azure [18]
• Forrester PaaS Reference Architecture [19]
• Gartner PaaS Reference Model [20]
• WSO2 Cloud-aware application and PaaS architecture [22]