SOAP

: This article is about a computer protocol. For the common cleaning mixture, see SOAP. For other uses of the acronym SOAP, see soap (disambiguation).

SOAP is a protocol (computing) for exchanging XML-based messages over a computer network, normally using HTTP. SOAP forms the foundation layer of the Web Services Protocol Stack, providing a basic messaging framework that more abstract layers can build on. SOAP facilitates the Service-Oriented Architecture architectural Design pattern (computer science).

There are several different types of messaging patterns in SOAP, but by far the most common is the Remote Procedure Call (RPC) pattern, where one network node (the client ) sends a request message to another node (the server ), and the server immediately sends a response message to the client.

=Overview=

SOAP originally was an acronym for Simple Object Access Protocol , but the acronym was dropped in Version 1.2 of the SOAP specification. Originally designed by Dave Winer, Don Box, Bob Atkinson, and Mohsen Al-Ghosein in 1998 with backing from Microsoft (where Atkinson and Al-Ghosein worked at the time), the SOAP specification is currently maintained by the XML Protocol Working Group of the World Wide Web Consortium.

==Transport methods==

HTTP was chosen as the primary application layer protocol for SOAP since it works well with today s Internet infrastructure; specifically, SOAP works well with network firewall (networking). This is a major advantage over other distributed protocols like GIOP/IIOP or DCOM which are normally filtered by firewalls.

XML was chosen as the standard message format because of its widespread acceptance by major corporations and open source development efforts. Additionally, a wide variety of freely available software development tool significantly ease the transition to a SOAP-based implementation.

The somewhat lengthy syntax of XML can be both a benefit and a drawback. Its format is easy for humans to read, but can be complex and slow down processing times. For example, CORBA, GIOP and DCOM use much shorter, binary message formats. On the other hand, hardware appliances are available to accelerate processing of XML messages. Binary XML (the use of the word XML is controversial here) is also being explored as a means for streamlining the throughput requirements of XML

=Structure of a SOAP message=

A SOAP message is contained in an envelope. Within this envelope are two additional sections: the header and the body of the message. SOAP messages use XML Namespace (programming).

The header contains relevant information about the message. For example, a header can contain the date the message is sent, or authentication information. It is not required, but, if present, must always be included at the top of the envelope.

==Example SOAP messages==

Here is an example of how a client might format a SOAP message requesting product information from a fictional warehouse web service. The client needs to know which product corresponds with the ID 827635:

827635

Here is how the warehouse web service might format its reply message with the requested product information:

Toptimate 3-Piece Set 827635 3-Piece luggage set. Black Polyester. 96.50 true

=See also=

==Related technologies==

*Comparison of Web service markup languages *List of Web service markup languages *Software componentry *Web service and some of its core technologies WSDL, UDDI *WS-I Basic Profile

==Alternatives to SOAP==

*Burlap [http://www.caucho.com/burlap/] *GXA *Hessian Web Service Protocol [http://www.caucho.com/hessian/index.xtp] *Representational State Transfer *XML-RPC

=External links=

*[http://www.xmlrpc.com/stories/storyReader$555 Dave Winer s history of SOAP] *[http://www.advogato.org/article/464.html Discussion on Web Services technology (SOAP and REST)] *[http://webservices.xml.com/pub/a/ws/2001/04/04/soap.html Don Box s history of SOAP] *[http://www.pocketsoap.com Simon Fell s PocketSOAP] and [http://www.pocketsoap.com/weblog/ his blog], which frequently covers contemporary SOAP topics *[http://dmoz.org/Computers/Programming/Internet/Web_Services/ SOAP Category at ODP] *[http://www.soaprpc.com/ws_implementations.html SOAP Implementations (list)] *[http://xml.coverpages.org/soap.html Technology Report] *[http://soap2corba.sourceforge.net/ Two-way SOAP to CORBA bridge] *[http://searchwebservices.techtarget.com/searchWebServices/downloads/what_is_soap.swf What is SOAP] (Macromedia_Flash presentation; requires plugin.) *[http://www.w3schools.com/soap/ W3Schools SOAP Tutorial] (Note: This is an outdated tutorial, which advocates the incorrect SOAP XML_namespace) *[http://www.w3.org/TR/soap12-part0/ W3C SOAP: Primer] *[http://www.w3.org/TR/soap12-part1/ W3C SOAP: Messaging Framework] *[http://www.w3.org/TR/soap12-part2/ W3C SOAP: Adjuncts] *[http://www.w3.org/2000/xp/ XML protocol activity]