SOAP Message Exchange Patterns
The SOAP specification mentions a concept called "message exchange patterns" (MEP). There are two basic message exchange patterns described in the SOAP specification:
- Request - Response
These two message exchange patterns are described in the following sections.
Request - Response
In a request - response message exchange the SOAP client sends a SOAP request message to the service. The service responds with a SOAP response message.
A request - response message exchange patterns is necessary when the SOAP client needs to send data to the SOAP service, for the service to carry out its job. For instance, if the client request that data be stored by the service, the client needs to send the data to be stored to the service.
Here is an illustration of a request - response message exchange:
|A SOAP request - response message exchange.|
In a response message exchange the SOAP client connects to the service, but does not send a SOAP message through. It just sends e.g. a simple HTTP request. The service responds with with a SOAP message.
This message exchange pattern is similar to how a browser communicates with a web server. The browser sends an HTTP request telling what page it wants to access, but the HTTP request does not carry any additional data. The web server responds with an HTTP response carrying the requested page.
Here is an illustration of the response message exchange pattern:
|A SOAP response message exchange.|