Resource Oriented Architecture (or, ROA) is a specific set of guidelines of an implementation of the REST

Rest

Rest may refer to:* Leisure* Human relaxation* SleepRest may also refer to:* Rest , a pause in a piece of music* Rest , the relation between two observers* Rest , a 2008 album by Gregor Samsa...

 architecture.

REST, or Representational State Transfer (see Roy Thomas Fielding's Doctoral Thesis "Architectural Styles and
the Design of Network-based Software Architectures" http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm), describes a series of architectural constraints that exemplify how the web's design emerged. Various concrete implementations of these ideas have been created throughout time, but it has been difficult to discuss the REST architecture without blurring the lines between actual software, or the architectural principals behind them.

In Chapter 5 of his thesis, Fielding documents how the World Wide Web is designed to be constrained by the REST series of limitations. These are still fairly abstract and have been interpreted in various ways in designing new frameworks, systems, and websites. In the past, heated exchanges have been made about whether RPC

Remote procedure call

In computer science, a remote procedure call is an inter-process communication that allows a computer program to cause a subroutine or procedure to execute in another address space without the programmer explicitly coding the details for this remote interaction...

-style REST architectures are RESTful.

Guidelines for Clarification

The Resource Oriented Architecture as documented by Leonard Richardson and Sam Ruby gives concrete advice on specific technical details. Naming these collections of guidelines "Resource Oriented Architecture" may allow developers to discuss the benefits of an architecture in the context of ROA.

Example guidelines include:

• Query string parameters are appropriate if they are inputs to a Resource which is an algorithm
  • Otherwise, these values should be moved into the URI
• Prefer pragmatic uses of putting data into URI, instead of using HTTP Headers
  • A resource can use file extension in the URI, instead of Content-Type negotiation
• RPC-style APIs are avoided in favor of Resources and protocols
• A representation of a resource should have many links to the other Resources in the application, so that a client can discover state transitions
• URI templates provide the technology behind specifying families of URI to clients.

Common Guidelines

Some guidelines are already common within the larger REST communities:

• Applications should expose many URIs (possibly an infinite number of them), one for each Resource (any resources in your applications should be unambiguously accessible via a unique URI)
• Cookies representing IDs into a server side session are not RESTful
• Combinations of resources (i.e. a particular account viewing results a particular database query) can be RESTful if (and only if) the combination can be represented as a URI.
• RESTful URIs should facilitate "cut & paste" (that's the notion of "transfer" of the "representational state")

Existing Frameworks

RESTful Web Services discusses many software frameworks which provide some or many features of the ROA. These include

• JBoss Seam
  JBoss Seam
  Seam is a web application framework developed by JBoss, a division of Red Hat.- Seam 3 :Seam 3 is very active project consisting of over 50 developers and engineers, which provides a modular set of extensions to the CDI programming model...
  
  
• JBoss RESTEasy
• Jersey JSR-311 or JAX-RS
• Ruby on Rails
  Ruby on Rails
  Ruby on Rails, often shortened to Rails or RoR, is an open source web application framework for the Ruby programming language.-History:...
  
  
• NetKernel
  NetKernel
  NetKernel is an implementation of the resource oriented computing abstraction.ROC is a logical computing model that resides on top of but is completely isolated fromthe physical realm of code and objects....
  
  
• Django and Turbogears
  TurboGears
  TurboGears is a Python web application framework consisting of several WSGI components such as Pylons, SQLAlchemy, Genshi and Repoze.TurboGears is designed around the model-view-controller architecture, much like Struts or Ruby on Rails, designed to make rapid web application development in Python...
  
  
• Restlet
  Restlet
  Restlet is a lightweight, comprehensive, open source REST framework for the Java platform. Restlet is suitable for both server and client Web applications. It supports major Internet transport, data format, and service description standards like HTTP and HTTPS, SMTP, XML, JSON, Atom, and WADL...
  
  
• Waves
• Symfony
  Symfony
  Symfony is a web application framework written in PHP which follows the model-view-controller paradigm. Released under the MIT license, Symfony is free software...
  
  
• Recess
• EverRest

Why the Web?

While REST is a set of architectural guidelines applicable to various types of computing infrastructures, Resource Oriented Architecture (ROA) is only coupled with the web. This architecture is therefore useful mostly to businesses that consider the web as the computing/publishing platform of choice.

The power of the web seems to mostly reside in its ability to lower the barriers to entry for human users who may not be highly trained in using computing machinery. As such, the web widens the market reach for any business that decides to publish some of its content in electronic format.

On the web, such published content is regarded as a resource

Resource (Web)

The concept of resource is primitive in the Web architecture, and is used in the definition of its fundamental elements. The term was first introduced to refer to targets of Uniform Resource Locators , but its definition has been further extended to include the referent of any Uniform Resource...

.

The World of Representations

Humans live in the world of representations. Representation, as a concept, is an attempt (arguably futile) to reach certain acceptable level of objectivity.

For example, if a person wants to buy a house, that person needs to qualify for a mortgage. If that person explains to the mortgage broker that he has $50,000.00 cash available for the down payment toward purchasing the house, the broker will not go ahead and approve the mortgage, even though the quoted amount would be fully satisfactory. What the mortgage broker needs is a more objective argument that would reassure the issuer that the party asking for the mortgage does indeed have enough money for the down payment.

But how is the issuer to go about obtaining the more objective proof? Certainly not by going directly into the applicant's safety vault and counting the money deposited there. Instead, the issuer is simply expecting to receive a representation of that person's balance in his bank account.

That representation projects a sufficient illusion of objectivity, so that the involved parties could sufficiently relax and that the business transaction can eventually take place.

In the same manner, any transaction that transpires on the web is based on the similar representational logic. The actual resource is never being touched. Instead, various representations of the said resource are being prepared, rendered, and shipped to the clients for consumption. Same as in the real world, where the mortgage issuer will never actually touch client's money, but will instead be satisfied with a mere piece of paper representing the balance, resources on the web never get to be directly manipulated by the clients.