BEGIN:VFREEBUSY ??? END:VFREEBUSY (If your fhir server provides this information via calDAV, then you may want to include addressing information in a URL section, and with the search, a DTSTART and DTEND component can be included to indicate the range of time that has been covered in the collection of slots, where these overlap the resources period values. For all slots that reference this resource, include a FREEBUSY row for each slot)
identifier
UID
active
serviceCategory
serviceType
n/a
specialty
actor
ATTENDEE:MAILTO:john_public@host2.com This can be populated with a value from the referenced resource
planningHorizon
DTSTART:20131201T003000Z DTEND:2014030101T003000Z
comment
COMMENT:(comment) If there is no comment, then the line can be excluded from the iCalendar entry