===== SOAP Cheat Sheet =====

SOAP is a popular protocol for accessing a web service. My interest in this arose when I needed to schedule a web service using the Oracle Scheduler. This SOAP client had to be written from scratch using PL/SQL so I needed to become familiar with the protocol first.

This is a summarized form of the [[http://www.w3schools.com/soap/default.asp| SOAP Tutorial]].

SOAP is an XML dialect so the [[XML Cheat Sheet]] might be useful and in particular the [[ xml_cheat_sheet#xml_namespaces | XML Namespaces section]] .

For reference here are the  [[http://www.w3.org/TR/soap/  | SOAP Specifications]] .

  * The  **S**imple **O**bject **A**ccess **P**rotocol  (SOAP) is a simple XML based protocol to let apps exchange information over HTTP.

  * SOAP is a W3C standard, the latest version is 1.2. SOAP is also a major part of .NET .


==== Messages ====

  * A SOAP message
    * MUST contain an envelope root element
    * MAY contain a header element
    * MUST contain a body element
    * MAY contain a fault element
    * MUST use the SOAP Envelope and a SOAP Encoding namespaces.

  * This is a sample SOAP message.
<code xml><?xml version="1.0"?>
<soap:Envelope
xmlns:soap="http://www.w3.org/2001/12/soap-envelope"
soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">

<soap:Header> ... </soap:Header>
<soap:Body>
  ...
  <soap:Fault> ... </soap:Fault>
</soap:Body>

</soap:Envelope></code>

==== Envelopes ====

  * There are three attributes in the SOAP envelope namespace :
    * actor - URI of endpoint for which the element is intended
    * mustUnderstand - 0 or 1 to specify whether the receiver is obligated to recognize the element or not.
    * encodingStyle

  * The SOAP Envelope namespace for elements must always be http://www.w3.org/2001/12/soap-envelope .

  * One possible SOAP Encoding namespace for SOAP encoding and data types is http://www.w3.org/2001/12/soap-encoding .

==== Fault Elements ====

The optional SOAP Fault element is used to hold error and status information for a SOAP message. It can have the following sub-elements :
  * faultcode - A code for identifying the fault. The faultcode must be one of the following :
    * VersionMismatch - Found an invalid namespace
    * MustUnderstand - A required element was not understood
    * Client - There was an error in the message
    * Server - There was an error on the server processing the message
  * faultactor - The endpoint that caused the fault
  * faultstring - A human-readable explanation
  * details - Application-specific error info