Cloud Definitions

The National Institute of Standards and Technology’s (NIST’s) Special Publication
800-145, “The NIST Definition of Cloud Computing,” defines the cloud as having
five essential characteristics:
1- On-demand self-service
2 - Broad network access
3 - Resource pooling
4 - Rapid elasticity
5 - Measured service

The publication also specifies three service models:
1 - Software as a Service (SaaS)
2 - Platform as a Service (PaaS)
3 - Infrastructure as a Service (IaaS)

And the document defines four deployment models:
1 - Private cloud
2 - Community cloud
3 - Public cloud
4 - Hybrid cloud

The NIST standard is freely available for use and remains the best definition of
cloud computing today, in part due to its simplicity and brevity. NIST has published
other cloud standards that are primarily aimed at departments and agencies
of the US Government, as well as cloud architecture document Special Publication
500-292, “NIST Cloud Computing Reference Architecture.” Larger enterprises might
find this document useful when planning adoption of the cloud.