This code system http://hl7.org/fhir/filter-operator defines the following codes:
| Code | Display | Definition |
| = | Equals | The specified property of the code equals the provided value. |
| is-a | Is A (by subsumption) | Includes all concept ids that have a transitive is-a relationship with the concept Id provided as the value, including the provided concept itself (i.e. include child codes) |
| descendent-of | Descendent Of (by subsumption) | Includes all concept ids that have a transitive is-a relationship with the concept Id provided as the value, excluding the provided concept itself (i.e. include child codes) |
| is-not-a | Not (Is A) (by subsumption) | The specified property of the code does not have an is-a relationship with the provided value. |
| regex | Regular Expression | The specified property of the code matches the regex specified in the provided value. |
| in | In Set | The specified property of the code is in the set of codes or concepts specified in the provided value (comma separated list). |
| not-in | Not in Set | The specified property of the code is not in the set of codes or concepts specified in the provided value (comma separated list). |
| generalizes | Generalizes (by Subsumption) | Includes all concept ids that have a transitive is-a relationship from the concept Id provided as the value, including the provided concept itself (e.g. include parent codes) |
| exists | Exists | The specified property of the code has at least one value (if the specified value is true; if the specified value is false, then matches when the specified property of the code has no values) |