Web Application Description Language

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The Web Application Description Language (WADL) is an XML-based file format that provides a machine-readable description of HTTP-based web applications. These applications are typically REST web services. WADL is a W3C Member Submission[1]

The purpose of WADL is to allow services on the internet (or any other IP network) to be described in a machine processable way, to make it easier to create Web 2.0 style applications and create a dynamic way of creating and configuring services. Prior to this, it was necessary to go to an existing web service, study it and write the application manually. WADL can be thought of as the REST equivalent of Web Services Description Language version 1.1. Version 2.0 of WSDL can be used to describe REST Web services[2], thus competing with WADL[citation needed].

WADL is intended for applications that are based on the existing architecture of the Web. Like WSDL, it is platform and language independent, and aims to promote re-use of applications beyond the basic use in a web browser. WADL models the resources provided by a service, and the relationships between them.

The service is described using a set of resource elements. Each of these contains param elements to describe the inputs, and method elements which describe the request and response of a resource. The request element specifies how to represent the input, what types are required and any specific HTTP headers that are required. The response describes the representation of the service's response, as well as any fault information, to deal with errors.

WADL is not yet widely supported. It has the advantage over the more complicated WSDL in that it does not impose any further level of abstraction on the service description; however, as tools become available for application development with WADL, it is likely they will include ways of automatically generating WADL, and this risks imposing an RPC style on it, going against the intended simplicity of WADL.


  1. http://www.w3.org/Submission/wadl/
  2. http://www.ibm.com/developerworks/webservices/library/ws-restwsdl/

External links

pl:Web Application Description Language

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