This code system http://hl7.org/fhir/action-relationship-type defines the following codes:

Code Display Definition
before-start Before Start The action must be performed before the start of the related action.
before Before The action must be performed before the related action.
before-end Before End The action must be performed before the end of the related action.
concurrent-with-start Concurrent With Start The action must be performed concurrent with the start of the related action.
concurrent Concurrent The action must be performed concurrent with the related action.
concurrent-with-end Concurrent With End The action must be performed concurrent with the end of the related action.
after-start After Start The action must be performed after the start of the related action.
after After The action must be performed after the related action.
after-end After End The action must be performed after the end of the related action.
<status value="draft"/> <experimental value="false"/> <date value="2021-01-05T10:01:24+11:00"/> <publisher value="HL7 (FHIR Project)"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> <telecom> <system value="email"/> <value value="fhir@lists.hl7.org"/> </telecom> </contact> <description value="Defines the types of relationships between actions."/> <caseSensitive value="true"/> <valueSet value="http://hl7.org/fhir/ValueSet/action-relationship-type"/> <content value="complete"/> <concept> <code value="before-start"/> <display value="Before Start"/> <definition value="The action must be performed before the start of the related action."/> </concept> <concept> <code value="before"/> <display value="Before"/> <definition value="The action must be performed before the related action."/> </concept> <concept> <code value="before-end"/> <display value="Before End"/> <definition value="The action must be performed before the end of the related action."/> </concept> <concept> <code value="concurrent-with-start"/> <display value="Concurrent With Start"/> <definition value="The action must be performed concurrent with the start of the related action."/> </concept> <concept> <code value="concurrent"/> <display value="Concurrent"/> <definition value="The action must be performed concurrent with the related action."/> </concept> <concept> <code value="concurrent-with-end"/> <display value="Concurrent With End"/> <definition value="The action must be performed concurrent with the end of the related action."/> </concept> <concept> <code value="after-start"/> <display value="After Start"/> <definition value="The action must be performed after the start of the related action."/> </concept> <concept> <code value="after"/> <display value="After"/> <definition value="The action must be performed after the related action."/> </concept> <concept> <code value="after-end"/> <display value="After End"/> <definition value="The action must be performed after the end of the related action."/> </concept> </CodeSystem>