Representational state transfer is an architectural paradigm. The key goals of REST include the following:

A RESTful Web API is a web API that conforms to the REST principles. The main principles of REST include:

The following sections will explain the popular REST-based service frameworks or APIs.

Ruby on Rails is an optimized open source web application framework that runs on top of the Ruby programming language. Ruby on Rails follows the basic software engineering patterns and principles. The Rails Web API is a framework that facilitates the creation of web applications based on the Model-View-Controller (MVC) framework. The View layer is composed of templates and most of these templates are HTML-based with embedded Ruby code. The Model layer represents the domain model, the business logic classes, and the data access classes. The Controller layer handles incoming HTTP requests. Note that the Rails controller can generate XML, JSON, PDFs, and also mobile-specific views. You can get more information on this framework from http://api.rubyonrails.org/.

Restlet provides support for an extensive list of extensions that include the following:

The benefits of Restlet include the following:

You can explore more on this API from http://restlet.org/discover/features.

The Django REST Framework provides a powerful and flexible API using which you can build Web APIs seamlessly. This API provides an extensive documentation and an excellent community support. You can know more on this framework from this link: http://django-rest-framework.org/.

The Flickr REST API is simple and easy to use. Flickr also has some JSON APIs that you might make use of for invoking the API through JavaScript. You can get more information in this regard from http://www.flickr.com/services/api/request.rest.html.

The Custom Search JSON/Atom API from Google enables developers to write applications that can leverage this API and retrieve and display custom search in the applications. This API allows you to use RESTful calls for web search and get the results in the JSON or Atom format. You can know more on this API from this https://developers.google.com/custom-search/json-api/v1/overview.

The Yahoo! REST APIs provide a collection of URI resources that can provide access to the following:

These URIs are actually grouped into APIs depending on the information they return. For more information, you can refer to the following site: http://developer.yahoo.com/social/rest_api_guide/web-services-intro.html.