An aspect of the present invention includes a protocol for conveying data during an e-commerce session with a polymorphic response, comprising initiating a session with a message from a buyer application to a broker application and a session identifier assigned by the broker application; conducting the session between the buyer application and a supplier application; and concluding the session with a additional message which includes a schema identifier for the additional message, resolvable in a context of a system identifier; and a polymorphic response comprising a type and a version, wherein the polymorphic response includes additional data elements corresponding to values assigned to the type and version.