Applications run on physical systems that aren't specified, data is stored in locations that are unknown, administration of systems is outsourced to others, and access by users is ubiquitous.

Insourced or Outsourced means whether the service is provided by the customer or the service provider.

In the SaaS model, the application is provided to the client through a thin client interface.

Microsoft's Windows Azure Platform is best described as currently using SaaS model.

The best-known service models are Software as a Service, Platform as a Service, and Infrastructure as a Service”the SPI model.

While cloud computing applications excel at large-scale processing tasks, if your application needs large amounts of data transfer, cloud computing may not be the best model for you.

When the service requires the client to use a complete hardware/software/application stack, it is using the most refined and restrictive service model.

Cloud computing is a stateless system, as is the Internet in general.