Platform-as-a-Service Reference Model

Platform-as-a-Service (PaaS) solutions offer a cloud-based platform that allows developers to create and deploy applications. They serve as the intermediary layer upon which applications are constructed.

The middleware's primary job is to manage applications. PaaS systems offer programs a runtime environment without providing any services for controlling the underlying infrastructure. They streamline the process of deploying applications to the infrastructure, setting up application components, provisioning and configuring supporting technologies like load balancers and databases, and overseeing system changes according to user-defined policies.

Developers primarily focus on designing their systems based on applications and do not have to worry about the underlying hardware, whether it is physical or virtual, operating systems, and other low-level services. The primary middleware is responsible for overseeing the allocation of resources and dynamically scaling applications based on user agreements. 

 

From a user perspective, the core middleware provides APIs that enable the programming and deployment of applications in the cloud. These can manifest as either a Web-based interface or as programming APIs and frameworks.

The different solutions can be classified into three broad categories: PaaS-I, PaaS-II, and PaaS-III. 

 

PaaS-I: 

 

The initial category pertains to PaaS solutions that fully adhere to the cloud computing paradigm for the development and deployment of applications. 

 

The platform provides a comprehensive development environment that is accessible through a web browser. This environment allows users to design, build, compose, and deploy applications. 

 

This pertains to the situation involving Force.com and Longjump. Both platforms provide a combination of middleware and infrastructure. 

 

PaaS-II: 

 

The second class comprises solutions that primarily aim to offer a scalable infrastructure for Web applications, particularly websites. 

 

In this scenario, developers typically utilize the application programming interfaces (APIs) provided by the providers. These APIs are constructed on top of robust runtimes specifically designed for industrial use, enabling developers to create applications. 

 

Google AppEngine is the leading offering in this area. The platform offers a scalable runtime environment that is built on the Java and Python programming languages. These languages have been adapted to provide a safe runtime environment and have been enhanced with new APIs and components to assist scalability. 

 

AppScale is an open-source version of Google AppEngine that requires the installation of interface-compatible middleware on a physical infrastructure. 

 

The Joyent Smart Platform offers a comparable methodology to that of Google AppEngine. Heroku and Engine 

 

Yard offer scalability support specifically for websites built with Ruby and Ruby on Rails. In this scenario, developers utilize conventional methodologies to design and construct their applications, which are subsequently deployed by uploading them onto the platform provided by the service provider. 

 

PaaS-III: 

 

The third category encompasses any systems that offer a cloud programming platform capable of supporting other types of applications, beyond just Web apps. Out of all these options, the most widely used is Microsoft Windows Azure. 

 

It offers a full framework for creating cloud applications that are service-oriented. 

 

These applications are built on top of the .NET technology and are hosted on Microsoft's datacenters. Other systems in the same category, such as Manjrasoft Aneka, Apprenda SaaSGrid, Appistry Cloud IQ Platform, DataSynapse, and GigaSpaces DataGrid, offer middleware with varying services.

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Happy Exploring!