Line 368 - Elsewhere it's recommended that intervals have DtStart and Duration (either of which can be filled in through eg inheritance), but we see later an odd blend (line 858 adds DtEnd to the mix). This needs to be clear and consistent across the doc.

Added language on the exclusivity, as well as that either is used to compute the Designated Interval's dtStart A Calendar Gluon may either have a dtStart or a dtEnd, but may not have both. DtStart is inherited by the Designated Interval. A Calendar Gluon may have either a dtStart or a dtEnd, but may not have both. DtEnd is inherited by the Designated Interval, in which it is used with the Bound Duration to compute the Bound dtStart.