Web Service

Web Services Fundamentals

Two Competing Approaches

  • REST-style
  • SOAP-style

Four Fundamental Technologies

  • XML
    • Describing information sent over the network
  • WSDL
    • Defining web service capability
  • SOAP
    • Accessing web services
  • UDDI
    • Finding web services

Web Service Infrastructure and Components

XML

  • Has emerged as the standard solution for describing information exchanged between heterogeneous system
  • Can be read by programs and interpreted in an application-specific way
  • Example
    • <Account>xx</Account>

WSDL: Describing the web service

  • Provides functional description of network services
    • IDL description
    • Protocol and deployment details
    • Platform independent description
    • Extensible language
  • As extended IDL: WSDL allows tools to generate compatible client and server stubs
    • Allows industries to define standardized service interfaces
    • Allows advertisement of service descriptions, enables dynamic discovery and binding of compatible services
      • Used in conjunction with UDDI registry
  • The main elements in a WSDL description

UDDI: Finding Web Service

  • Universal Description, Discovery, Integration
  • UDDI defines the operation of a service registry
    • Data structures for registering
      • Business
      • Technical specification: tModel is a keyed reference to a technical sepcifcaiton
      • Service and service endpoints
        • Referencing the supported tModels
  • The main UDDI data structures

SOAP

  • Why SOAP
    • A “wire protocol” necessary for accessing distributed object services
    • Vendor and/or platform-specific wire protocols hinder interoperability
  • SOAP
    • An Internet standard specification, the goal of which is to define a platform and vendor-neural WIRE PROTOCOL based on Internet standard protocols [HTTP & XML] to access Web Services. 
  • Features
    • Uses XML to package requests for services exposed by Web Services, and responds generates by Web services
    • Typically uses HTTP as a transport protocol
  • SOAP message
    • Convey documents
    • Support client-server communication

RESTful Approach

  • Focus on using HTTP operations (GET, PUT, POST, DELETE) to manipulate data resources represented in XML
    • No WSDL + SOAP

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