PaaS | Platform as a service

1. PaaS stands for platform as a service.
2. PaaS provides a computing platform with a programming language execution environment.
3. PaaS provide a development and deployment platform for running applications in the cloud. 
4. PaaS constitute the middleware on top of which applications are built.
5. Application management is the core functionality of the middleware.
6. PaaS provides run time environments for the applications.
7. PaaS provides
   • Applications deployment
   • Configuring application components
   • Provisioning and configuring supporting technologies 
8. For users PaaS interfaces can be in the form of a Web-based interface or in the form of programming APIs and libraries.
9. PaaS solutions generally include the infrastructure as well.
10. PurePaaS offered only the user-level middleware.
11. PaasS classification:
    1. PaaS-I:  Runtime environment with Web-hosted application development platform. Rapid application prototyping. For example Force.com which is a combination of middleware and infrastructure product type.
    2. PaaS-II: Runtime environment for scaling Web applications. The runtime could be enhanced by additional components that provide scaling capabilities. For example Google AppEngine which is a combination of middleware and infrastructure product type. Appscale is middlware product type.
    3. PaaS-III: Middleware and programming model for developing distributed applications in the cloud. For example Microsoft Azure which is a combination of middleware and infrastructure product type. Manjrasoft Aneka is a middleware product type.
12. Some examples:
    • Google App Engine
    • Force.com

Characterstics of PaaS:

1. Runtime framework: The runtime framework executes end-user code according to the policies set by the user and the provider. 
2. Abstraction: PaaS offer a way to deploy and manage applications on the cloud rather than a virtual machines on top of which the IT infrastructure is built and configured. 
3. Automation: PaaS deploy the applications automatically.
4. Cloud services: Provide services for creation, delivery, monitoringm management, reporting of applications.