SOAP 1.2
Message Exchange Patterns (MEPs)

Glen Daniels

Jean-Jacques Moreau

SOAP 1.1

• HTTP specific
  • Although less so than prior versions
• Uses HTTP POST
• Mainly used for RPCs
  • RPC request mapped to HTTP request
  • RPC response mapped to HTTP response

SOAP 1.2

• No longer limited to HTTP
• Binding framework
  • Shields SOAP from underlying protocol
  • Model for plugging-in other protocols
  • Not limited to request-response either
  • Features not supported by a given protocol can be implemented via extensions to SOAP processing model

SOAP 1.2 MEPs

• Describe message exchanges, such as request-response
• Described by state machine for each participating node
• Independent of underlying protocol
• Named by URI
  • E.g. http://www.w3.org/2001/12/soap/mep/request-response/
• Two MEPs in latest ed-copy
  • SOAP request-response (stable)
  • SOAP response (work in progress, no consensus, subject to TAG feedback)
    • Web-friendly

Request-Response MEP

• Exchange of a single SOAP request and a SOAP response between two adjacent SOAP nodes
  • No intermediary in between
  • Assumption time-limited exchange, not long-lived transactions
    • Both requests and responses are SOAP messages
    • Both are processed according to SOAP processing model
• For HTTP binding, maps to HTTP POST

Request-Response MEP

Request-Response MEP

MEP properties:

• context:ExchangePatternName
• context:FailureReason
• reqres:Role
• reqres:State
• reqres:OutboundMessage
• reqres:InboundMessage
• reqres:ImmediateDestination
• reqres:ImmediateSender

SOAP MEP = WSDL MEP ?

Does it make sense to replace hard-coded <input> and <output> elements with dynamic syntax using SOAP message and feature names?

Example

<operation name="foo" mep="…/request-response">
  <message name="…OutboundMessage" element="foo:req" />
  <message name="…InboundMessage" element="foo:resp" />
</operation>