http://terminology.hl7.org/CodeSystem/v3-ActRelationshipType| Code | Display | Definition |
| COMP | has component | The target act is a component of the source act, with no semantics regarding composition or aggregation implied. |
| DRIV | is derived from | Associates a derived Act with its input parameters. E.G., an anion-gap observation can be associated as being derived from given sodium-, (potassium-,), chloride-, and bicarbonate-observations. The narrative content (Act.text) of a source act is wholly machine-derived from the collection of target acts. |
| RPLC | replaces | A replacement source act replaces an existing target act. The state of the target act being replaced becomes obselete, but the act is typically still retained in the system for historical reference. The source and target must be of the same type. |
| USE | uses | Indicates that the source act makes use of (or will make use of) the information content of the target act. *UsageNotes:* A usage relationship only makes sense if the target act is authored and occurs independently of the source act. Otherwise a simpler relationship such as COMP would be appropriate. *Rationale:* There is a need when defining a clinical trial protocol to indicate that the protocol makes use of other protocol or treatment specifications. This is stronger than the assertion of "references". References may exist without usage, and in a clinical trial protocol is common to assert both: what other specifications does this trial use and what other specifications does it merely reference. |
| XCRPT | Excerpts | The source is an excerpt from the target. |
| XFRM | transformation | Used when the target Act is a transformation of the source Act. (For instance, used to show that a CDA document is a transformation of a DICOM SR document.) |