Some SOAP Receivers using this binding might need certain information to be readily available within the underlying protocol. This binding uses the SOAPAction HTTP request header field to supply this information.
soapaction = "SOAPAction" ":" <"> URI-reference <">
The value of this request header field can be any URI reference, including absolute URIs and relative URIs, in which case it is interpreted relative to the Request-URI.
SOAPAction's presence in this binding's request messages is OPTIONAL. SOAP Receivers MAY use it as a hint to optimise processing, but SHOULD NOT require its presence in order to operate.
If a SOAP Receiver does require SOAPAction's presence in order to operate, it MUST respond to requests which either contain an unrecognised SOAPAction header value or do not contain a SOAPAction header with a 427 "SOAPAction Required" HTTP response status code. Such response messages MAY contain a 'Required-SOAPAction' HTTP response header field, whose value is the URI which can be used in the SOAPAction request header field to re-submit the request.
req-soapaction = 'Required-SOAPAction' ":" <"> URI-reference <">
Support for SOAPAction is OPTIONAL in implementations. Implementations SHOULD NOT generate or require SOAPAction UNLESS they have a particular purpose for doing so (e.g., a SOAP Receivers specifies its use).