The three Types of Cloud Computing Service Models are:
Software as a Service (SaaS)
The capability provided to the consumer is to use the provider‘s applications running on a cloud infrastructure. The applications are accessible from various client devices through either a thin client interface, such as a web browser (e.g., web-based email), or a program interface. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.
Platform as a Service (PaaS)
The capability provided to the consumer is to deploy onto the cloud infrastructure consumer- created or acquired applications created using programming languages, libraries, services, and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly configuration settings for the application-hosting environment.
Infrastructure as a Service (IaaS)
The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, and deployed applications; and possibly limited control of select networking components (e.g., host firewalls).
The key features of PaaS are as follows:
• Multi-tenant architecture
• Customizable /Programmable User Interface
• Unlimited Database Customization
• Robust Workflow engine/capabilities
• Granular control over security/sharing (permissions model)
• Flexible ―services-enabled‖ integration model