While the marked are starting to get their grips on terminology and categorization of Cloud Computing, Gartner seem to be lost in their own world. Failing to separate Key characteristics, delivery models (Details here
) and deployment models and leveling the field into five attributes, Gartner tries to push us back to Ground Zero 
*A much better approach to see how strongly a cloud solution (or service) adheres to the cloud computing model would be to discuss the combination's in the figure above. *
The five attributes of cloud computing are:
Service-Based: Consumer concerns are abstracted from provider concerns through service interfaces that are well-defined. The interfaces hide the implementation details and enable a completely automated response by the provider of the service to the consumer of the service. The service could be considered "ready to use" or "off the shelf" because the service is designed to serve the specific needs of a set of consumers, and the technologies are tailored to that need rather than the service being tailored to how the technology works. The articulation of the service feature is based on service levels and IT outcomes (availability, response time, performance versus price, and clear and predefined operational processes), rather than technology and its capabilities. In other words, what the service needs to do is more important than how the technologies are used to implement the solution.
Scalable and Elastic: The service can scale capacity up or down as the consumer demands at the speed of full automation (which may be seconds for some services and hours for others). Elasticity is a trait of shared pools of resources. Scalability is a feature of the underlying infrastructure and software platforms. Elasticity is associated with not only scale but also an economic model that enables scaling in both directions in an automated fashion. This means that services scale on demand to add or remove resources as needed.
Shared: Services share a pool of resources to build economies of scale. IT resources are used with maximum efficiency. The underlying infrastructure, software or platforms are shared among the consumers of the service (usually unknown to the consumers). This enables unused resources to serve multiple needs for multiple consumers, all working at the same time.
Metered by Use: Services are tracked with usage metrics to enable multiple payment models. The service provider has a usage accounting model for measuring the use of the services, which could then be used to create different pricing plans and models. These may include pay-as-you go plans, subscriptions, fixed plans and even free plans. The implied payment plans will be based on usage, not on the cost of the equipment. These plans are based on the amount of the service used by the consumers, which may be in terms of hours, data transfers or other use-based attributes delivered.
Uses Internet Technologies: The service is delivered using Internet identifiers, formats and protocols, such as URLs, HTTP, IP and representational state transfer Web-oriented architecture. Many examples of Web technology exist as the foundation for Internet-based services. Google's Gmail, Amazon.com's book buying, eBay's auctions and Lolcats' picture sharing all exhibit the use of Internet and Web technologies and protocols.