This attribute is an optional string for QDoc requests at the root element level that designates a requestor-defined identifier. It is used only in conjunction with the logTransaction attribute. It is entirely requestor-defined, and does not have to be a unique key. The intent is to capture its value in any QDoc log entries, so that remote requestors can refer to an audit trail entry in case of internal communication failures.
Note: Because there is no equivalent of the transactionID attribute in the QDoc 1.1 syntax specification, transactionID has been removed from that version of the syntax.