| TransactionActionCode | To specify the type of action requested when more than one function could be handled by the message. |
| AltLangID | The alternate language for a customer or message encoded as ISO 639-3. |
| CorrelationID | Allows end-to-end correlation of log messages with the corresponding Web service message throughout the processing of the Web service message. |
| EchoToken | A reference for additional message identification, assigned by the requesting host system. |
| PrimaryLangID | The primary language preference for the message encoded as ISO 639-3. |
| RetransmissionIndicator | When true, indicates the message is being re-sent after a failure. |
| SequenceNmbr | The sequence number of the transaction assigned by the sending system for ordered message processing or message resynchronization. |
| Target | Test or Production target system indicator. |
| TargetName | The name of the Test or Production system. |
| TimeStamp | ISO 8601 encoded timestamp indicating the creation date and time of the message. |
| TransactionIdentifier | Unique identifier to relate all messages within a transaction (e.g. this would be sent in all request and response messages that are part of an on-going transaction). |
| TransactionStatusCode | This indicates where this message falls within a sequence of messages. |
 Version | The OpenTravel message version indicated by a decimal value. |
ReservationPayment