This case-sensitive code system http://hl7.org/fhir/map-source-list-mode defines the following codes:
| Code | Display | Definition |
| first | First | Only process this rule for the first in the list |
| not_first | All but the first | Process this rule for all but the first |
| last | Last | Only process this rule for the last in the list |
| not_last | All but the last | Process this rule for all but the last |
| only_one | Enforce only one | Only process this rule is there is only item |