This is specifically considered out of scope for this IG and consider an implementation specific process. See http://build.fhir.org/ig/HL7/davinci-alerts/index.html#scope-and-usage "What constitutes a trigger (nature of the event as defined in your organization)" it is assumed a trigger is not only What event occurred but also for whom and about who. Will add a sub-bullet to trigger or separate to define what is meant by trigger (what event, who is about ,who does it go to) In future version of this IG we may leverage or reference the work done by Subscriptions for defining triggering.