Web Services

What is XML?

  • XML stands for EXtensible Markup Language
  • XML is a markup language much like HTML
  • XML was designed to carry data, not to display data
  • XML tags are not predefined. You must define your own tags

XML was designed to transport and store data.

HTML was designed to display data.

What is SOAP?

SOAP is an XML-based protocol to let applications exchange information over HTTP.

Or more simple: SOAP is a protocol for accessing a Web Service.

  • SOAP stands for Simple Object Access Protocol
  • SOAP XML based message exchange
  • SOAP uses different transport protocols, such as HTTP and SMTP
  • SOAP is a standard communication protocol
  • SOAP is a format for sending messages
  • SOAP is designed to communicate via Internet
  • SOAP is platform independent
  • SOAP is language independent
  • SOAP is simple and extensible
  • SOAP allows you to get around firewalls







  • A WSDL is an XML document that describes a web service. It actually stands for Web Services Definition Language. SOAP is an XML-based protocol that lets you exchange info over a particular protocol (can be HTTP or SMTP)
  • WSDL is often used in combination with SOAP and XML Schema to provide web services over the Internet. A client program connecting to a web service can read the WSDL to determine what functions are available on the server. Any special datatypes used are embedded in the WSDL file in the form of XML Schema.
  • A WSDL document has a definitions element that contains the other five elements, types, message, portType, binding and service. The following sections describe the features of the generated client code. WSDL supports the XML Schemas specification (XSD) as its type system.

WSDL Documents

An WSDL document describes a web service. It specifies the location of the service, and the methods of the service, using these major elements:

Element Description
<types> Defines the (XML Schema) data types used by the web service
<message> Defines the data elements for each operation
<portType> Describes the operations that can be performed and the messages involved.
<binding> Defines the protocol and data format for each port type

Notational Conventions :

The following namespace prefixes are used throughout this document:

prefix namespace URI definition
wsdl http://schemas.xmlsoap.org/wsdl/ WSDL namespace for WSDL framework.
soap http://schemas.xmlsoap.org/wsdl/soap/ WSDL namespace for WSDL SOAP binding.
http http://schemas.xmlsoap.org/wsdl/http/ WSDL namespace for WSDL HTTP GET & POST binding.
mime http://schemas.xmlsoap.org/wsdl/mime/ WSDL namespace for WSDL MIME binding.
soapenc http://schemas.xmlsoap.org/soap/encoding/ Encoding namespace as defined by SOAP 1.1 [8].
soapenv http://schemas.xmlsoap.org/soap/envelope/ Envelope namespace as defined by SOAP 1.1 [8].
xsi http://www.w3.org/2000/10/XMLSchema-instance Instance namespace as defined by XSD [10].
xsd http://www.w3.org/2000/10/XMLSchema Schema namespace as defined by XSD [10].
tns (various) The “this namespace” (tns) prefix is used as a convention to refer to the current document.
(other) (various) All other namespace prefixes are samples only. In particular, URIs starting with “http://example.com” represent some application-dependent or context-dependent URI [4].


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