Academy & Industry Research Collaboration Center
Cloud computing refers to both the applications delivered as services over the Internet and the hardware and systems software in the data centers that provide those services. These services have long been referred to as Software as a Service (SaaS). Some terms such as PaaS (Platform as a Service) and IaaS (Infrastructure as a Service) are used by vendors to describe their products, but the authors avoid these because accepted definitions for them still vary widely. There is no crisp line between "Low-level "Infrastructure and a higher-level "Platform ". They believe both of these are more alike than different, and they do consider them together.