Simple Object Access Protocol

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What Does Simple Object Access Protocol Mean?

Simple Object Access Protocol (SOAP) is a protocol for implementing Web services. SOAP features guidelines that allow communication via the Internet between two programs, even if they run on different platforms, use different technologies and are written in different programming languages.


Today, this term is simply known as SOAP and is not considered an acronym.

Techopedia Explains Simple Object Access Protocol

As a protocol, SOAP has four basic parts:

  • Guidelines for the contents of a message and how it is processed
  • Encoding guidelines for application-defined data types
  • Guidelines for remote procedure calls (RPCs) and responses
  • Guidelines for exchanging messages through certain protocols

SOAP is written using Extensible Markup Language (XML). The XML document structure is therefore also made up of four basic elements:

  • Envelope
  • Header
  • Body
  • Fault

The envelope element is where an XML document can be identified as a SOAP message. A SOAP message is an XML document structured with the envelope element encapsulating both the header element and the body element, in that order. The fault element is located within the body.

The header element is actually optional. But when present, it is where information may be found about the application, such as authentication, payment, transaction ID, etc.

The body element is where the actual message is found. The fault element contains errors and status information.

Although SOAP messages use HTTP as their delivery system, other transport protocols are also supported.


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Margaret Rouse
Senior Editor
Margaret Rouse
Senior Editor

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.