SOAP and REST.

Web Services

• Transport Protocols : SOAP, REST
• Respective registries to shared data.
• Message integrity and non-repudiation
• Reliable messaging
• Business process flow
• Protocol negotiation
• Security
• Transactions and process flow
• Data independence for programming languages, middle-ware systems and DBMS
• typing
• structure
• semantic information associated with data (mapping, transformation, creation)

Components for Web Services

• XML: Extensible Markup Language
• WSDL : fundamental abstraction of Web services as interface to underlying software
• SOAP/REST : communication protocol over internet and networks
• UDDI : Providing registry and repository services for storing and retrieving Web services interfaces

WSDL : Web Services Description Language

• A mechanism to describe Web Services
• data types
• data structures
• define interfaces
• associate services with underlying implementations in each interface
• how to map the types and structures into the messages to be exchanged
• how to tie the messages to underlying implementations
• A definition of service to map to communication protocols and transports such as SOAP messages.
• both parties interact by sharing a common WSDL file.
• sender uses the WSDL file to generate the messages.
• receiver uses the WSDL file to parse the message and map it to underlying program.
• The goal is that the parts can be developed separately and integrated as a comprehensive WSDL file.

UDDI : Universal Description, Discovery, and Integration

SOAP : Simple object Access Protocol

• Understanding SOAP from IBM
• Defines a common format for XML messages over HTTP and other protocols.
• SOAP is designed so that it can be extended to additional features and functions.
• SOAP is a one-way asynchronous messaging technology.
• SOAP can be used in various messaging styles, from RPC (remote procedure calls) to document oriented publishing and subscription.
• Minimum criterion for a Web service must support SOAP.

Example of Simple SOAP Envelope

<?xml version='1.0' ?>
<env:envelope xmlns:env="http://www.w3.org/2003/05/SOAP-envelope"> 
  <env:header>
  </env:header>
  <env:body>
  </env:body>
</env:Envelope>

Example of SOAP Header with Routing Information

<?xml version='1.0' ?>
<env:Envelope xmlns:env="http://www.w3.org/2003/05/SOAP-envelope"> 
  <env:header>
    <wsa:ReplyTo xmlns:wsa=
        "http://schemas.xmlSOAP.org/ws/2004/08/addressing">
      <wsa:Address>
         http://schemas.xmlSOAP.org/ws/2004/08/addressing/role/anonymous
      </wsa:Address>
    </wsa:ReplyTo>
  </env:header>
  <env:body>
  </env:body>
</env:Envelope>

REST, RESTlet, RESTful : REpresentation State Transfer