SOAP

• Simple Object Access Protocol
  
• Protocol for exchanging XML-based messages over a network, usually using HTTP
• Makes it possible to get around firewalls and proxy servers
  
• Platform and language independent
• Based on XML

• The most common messaging pattern is RPC (Remote Procedure Call).
• SOAP is roughly 10 times as slow as binary network protocols (like RMI).
  

SOAP Messages

• A SOAP message is in an envelope.
  
• The envelope contains an optional header and the body of the message.
• SOAP messages use XML namespaces.

• Envelope element (required): Identifies the XML document as a SOAP message
• Header element (optional)
• Body element (required)
• Fault element (optional)
  
  
• Uses the SOAP Envelope namespace
• Uses the SOAP Encoding namespace

• Does not contain a DTD reference
• Does not contain XML Processing Instructions

Examples

<?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>