| Continuation | Specifies that this is a followup request asking for more of what was requested in the previous request. |
| End | This is the last message within a transaction. |
| InSeries | This is any message that is not the first or last message within a transaction. |
| Rollback | This indicates that all messages within the current transaction must be ignored. |
| Start | This is the first message within a transaction. |
| Subsequent | This request message is a subsequent request based on the previous message sent in this transaction. |