A quantity specifying a point on the axis of natural time. A point in time is most often represented as a calendar expression.

If a value is an exceptional value (NULL-value), this specifies in what way and why proper information is missing.

A quantity specifying a point on the axis of natural time. A point in time is most often represented as a calendar expression.

Specifies whether the limit is included in the interval (interval is closed) or excluded from the interval (interval is open).

A code specifying whether the set component is included (union) or excluded (set-difference) from the set, or other set operations with the current set component and the set as constructed from the representation stream up to the current point.

This is the low limit of the interval.

This is the high limit of the interval.

The difference between high and low boundary. The purpose of distinguishing a width property is to handle all cases of incomplete information symmetrically. In any interval representation only two of the three properties high, low, and width need to be stated and the third can be derived.

The arithmetic mean of the interval (low plus high divided by 2). The purpose of distinguishing the center as a semantic property is for conversions of intervals from and to point values.