From http://www.w3schools.com (Copyright Refsnes Data)

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 communicates 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 is a W3C recommendation

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.

SOAP is a W3C Recommendation

SOAP became a W3C Recommendation 24. June 2003.

To read more about the SOAP activities at W3C, please read our W3C Tutorial.