Introduction to SOAP

SOAP is a simple XML based protocol to let applications exchange information over HTTP.
Or more simply: SOAP is a protocol for accessing a Web Service.

What You Should Already Know

Before you study SOAP you should have a basic understanding of XML and XML Namespaces.

If you want to study these subjects first, please read our XML Tutorial.

What is SOAP?

• SOAP stands for Simple Object Access Protocol
• SOAP is a communication protocol
• SOAP is for communication between applications
• SOAP is a format for sending messages
• SOAP is designed to communicate via Internet
• SOAP is platform independent
• SOAP is language independent
• SOAP is based on XML
• SOAP is simple and extensible
• SOAP allows you to get around firewalls
• SOAP will be developed as a W3C standard

Why SOAP?

It is important for application development to allow Internet communication between programs.
Today's applications communicate using Remote Procedure Calls (RPC) between objects like DCOM and CORBA, but HTTP was not designed for this. RPC represents a compatibility and security problem; firewalls and proxy servers will normally block this kind of traffic.
A better way to communicate between applications is over HTTP, because HTTP is supported by all Internet browsers and servers. SOAP was created to accomplish this.
SOAP provides a way to communicate between applications running on different operating systems, with different technologies and programming languages.

Microsoft and SOAP

SOAP is a key element of Microsoft's .NET architecture for future Internet application development.

SOAP 1.1 was Proposed to W3C

UserLand, Ariba, Commerce One, Compaq, Developmentor, HP, IBM, IONA, Lotus, Microsoft, and SAP proposed to W3C, in May 2000, the SOAP Internet protocol that they hope will revolutionize application development by connecting graphic user interface desktop applications to powerful Internet servers using the standards of the Internet: HTTP and XML.

W3C is Working on SOAP 1.2

The first public Working Draft on SOAP was published from W3C in December 2001. To read more about the SOAP activities at W3C please visit our W3C tutorial.