Include text (taken from the model notes edited):
The Vavailability class includes a partially specified interval in which all blocks of granularity size are busy per the busy attribute - BUSY, BUY-UNAVAILABLE, BUSY-TENTATIVE.
The timeRange is "busy" for the purposes of a specific use. The class TimeRangeType MAY have a start time (optional), and if a start time is present MAY contain a duration (optional). It can accordingly apply to
(1) all time (no dtStart, no duration)
(2) a half-infinite interval (dtStart, no duration)
(3) a bound interval (dtStart, duration)
The optional granularity that MAY be present describes the time blocks used for expressing Availability--for example, for one hour blocks, use P1H.
Against this backdrop, The associate AvailabilityType objects indicate available times with an AvailabilityIntervalType having dtStart, duration, and optional tz.