Existing Wording: Period.start: If the low element is missing, the meaning is that the low boundary is not known.

Period.end: If the end of the period is missing, it means that the period is ongoing

Comment:

Clarify that "if the end is missing, it means that the period is ongoing" should be interpreted in the context of when the resource was created. The interpretation should be that it was ongoing at the time the resource was created, but may or may not have stopped by now.

It also seems odd that Period.start is not defned as parallel to Period.end. If missing, Period.start means we don't know when it started. If missing, Period.end means it is on going, and not that we don't know when it will end.

Summary:

Clarify Period.end missing implications.