The Online Resource URL of the request message is determined form the Capabilities XML returned by a GetCap request. The URL can be determined by the following XPATH expression: /FISHXML_Capabilities/capability/request/[Operation]/DCPType/HTTP/post/@xlink:href where [Operation] is the name of the HEEP Operation: 'getCap', 'getData', or 'getQuerySummary'. Note that the XPATH above is provided for convenience; HEEP services shall not be required to support XPATH parsing.

An XML document conforming with the FishXML_Request schema is constructed.

The above document is sent to above OnlineResource accoring to POST rules define by [IETF RFC 2616]. The XML document shall be accompanied by the header: Content-Type: text/xml; charset="utf-8". Note that a SOAP envelope is not employed.

An XML response is received form the HEEP server in a proscribed format, noted below.