These values are interpreted as follows: <br/>- "unknown" indicates that no specific value for temporal position is provided.<br/>- "now" indicates that the specified value shall be replaced with the current temporal position whenever the value is accessed.<br/>- "before" indicates that the actual temporal position is unknown, but it is known to be before the specified value.<br/>- "after" indicates that the actual temporal position is unknown, but it is known to be after the specified value.<br/>A value for indeterminatePosition may <br/>- be used either alone, or <br/>- qualify a specific value for temporal position.<br/>