Structure of SOAP Messages

SOAP messages are constructed using a framework that describes what is in a SOAP message, and how it should be processed. This is known as the SOAP envelope.

SOAP messages may contain encoding rules, which express instances of application‑defined data types. Remote procedure calls and responses are also described in a SOAP message. As mentioned earlier, there are two types of SOAP messages:

• Request messages ask a remote process to perform some sort of processing.

• Response messages are replies from a remote process that return data or an error message that indicates why the request could not be processed.

The payload contains data in XML format that is passed to or from a function. Request payloads contain everything needed to execute a function, including data and arguments passed as parameters. Response payloads contain the values that are returned from a function. SOAP uses XML to express payload information accurately and concisely. Every SOAP message has a main envelope section, which can contain header and body sub-sections.