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

LvlCodeDisplayDefinition
1named-event Named EventThe trigger occurs in response to a specific named event, and no other information about the trigger is specified. Named events are completely pre-coordinated, and the formal semantics of the trigger are not provided.
1periodic PeriodicThe trigger occurs at a specific time or periodically as described by a timing or schedule. A periodic event cannot have any data elements, but may have a name assigned as a shorthand for the event.
1data-changed Data ChangedThe trigger occurs whenever data of a particular type is changed in any way, either added, modified, or removed.
2  data-added Data AddedThe trigger occurs whenever data of a particular type is added.
2  data-modified Data UpdatedThe trigger occurs whenever data of a particular type is modified.
2  data-removed Data RemovedThe trigger occurs whenever data of a particular type is removed.
1data-accessed Data AccessedThe trigger occurs whenever data of a particular type is accessed.
1data-access-ended Data Access EndedThe trigger occurs whenever access to data of a particular type is completed.
<status value="draft"/><experimental value="false"/><date value="2023-03-26T15:21:02+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="The type of trigger."/><jurisdiction><coding><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><caseSensitive value="true"/><valueSet value="http://hl7.org/fhir/ValueSet/trigger-type"/><content value="complete"/><concept><code value="named-event"/><display value="Named Event"/><definition value="The trigger occurs in response to a specific named event, and no other information about the trigger is specified. Named events are completely pre-coordinated, and the formal semantics of the trigger are not provided."/></concept><concept><code value="periodic"/><display value="Periodic"/><definition value="The trigger occurs at a specific time or periodically as described by a timing or schedule. A periodic event cannot have any data elements, but may have a name assigned as a shorthand for the event."/></concept><concept><code value="data-changed"/><display value="Data Changed"/><definition value="The trigger occurs whenever data of a particular type is changed in any way, either added, modified, or removed."/><concept><code value="data-added"/><display value="Data Added"/><definition value="The trigger occurs whenever data of a particular type is added."/></concept><concept><code value="data-modified"/><display value="Data Updated"/><definition value="The trigger occurs whenever data of a particular type is modified."/></concept><concept><code value="data-removed"/><display value="Data Removed"/><definition value="The trigger occurs whenever data of a particular type is removed."/></concept></concept><concept><code value="data-accessed"/><display value="Data Accessed"/><definition value="The trigger occurs whenever data of a particular type is accessed."/></concept><concept><code value="data-access-ended"/><display value="Data Access Ended"/><definition value="The trigger occurs whenever access to data of a particular type is completed."/></concept></CodeSystem>