• SI2
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Objectives

To look at one of the controversies ranging around "Web2.0" and "Web services" - REST vs SOAP.

Background

WWW

• What in fact is it?

  "The Web’s major goal was to be a shared information space through which people and machines could communicate.” 
   - T. Berners-Lee
     WWW: Past, present, and future. IEEE Computer, 29(10), Oct. 1996, pp. 69–77
  

Needs addressed

• To share your own information.
• To access other people's information.

WWW innovations

• URL / URI (Uniform Resource Locator / Indicator)
  • Unique WWW address for every resource.
• HTTP (Hyper Text Transfer Protocol)
  • Protocol for transferring resource information between machines.

  • Request resource addressed by URI.

  • Receive representation of that resource.
    • In HTML, XML, text, whatever.

Formalization as REST

• Roy Fielding's doctoral thesis, 2000

  Representational State Transfer is intended to evoke an image of how a well-designed Web application behaves: a network of web pages (a virtual state-machine), where the user progresses through an application by selecting links (state transitions), resulting in the next page (representing the next state of the application) being transferred to the user and rendered for their use. 
     — Dr. Roy Fielding, Architectural Styles and the Design of Network-based Software Architectures
  

• Resources considered as "nouns".
  • Unlimited in number.
• HTTP actions considered as "verbs" acting on the nouns.
  • Restricted in number
    • GET
    • POST
    • PUT
    • DELETE

The schism - back to the past

• XML-RPC / SOAP (Remote Procedure Call / Simple Object Application Protocol / Service Oriented Application...)
• aka WSDL (Web Services Description Language) or even WS-*
  • Verb-oriented
    • Client requests service to carry out some operation.
    • No limit to number of verbs possible.

Example

• Analogy to programming languages.
• Nouns are data (variables).
  • Eg, dog, employee, salary, birthday
• Verbs...

  REST

  get(dog), get(employee),..., post(salary), post(birthday),...

  • exactly four (4) methods

  SOAP

  dogGet(), employeeGet(),..., salaryPost(), birthdayPost(),...

  • N methods

REST vs SOAP / WS-*

Web Services based on SOAP and WSDL are "Web" in name only. In fact, they are a hostile overlay of the Web based on traditional enterprise middleware architectural styles that has fallen far short of expectations over the past decade. 
  - Nick Gall, VP Gartner

So what is the role of SOAP?  SOAP is best utilized in closed systems (systems where all participants are known beforehand).  In a closed system each participant can be customized to understand the APIs of the other participants and can be optimized for maximum efficiency. 
  - Roger Costello

By the way, so why is anybody surprised that the open source community tends towards REST and big commercial interests tend towards SOAP? 
  - Johannes Ernst's Blog

REST vs SOAP / WS-*

The Rebels vs. the Empire... 
The enemy keeps changing. Bloated 'enterprise' technology has constantly changed form to try and outwit us. First DCE, then CORBA, next J2EE and now:
  - Duncan Cragg

Resources

• REST - Roger Costello

• The S stands for Simple - Pete Lacey

• How I Explained REST to My Wife - Ryan Tomayko

• Representational_State_Transfer - Wikipedia

• Roots of the REST/SOAP Debate - Paul Prescod

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