E93 Presence in Version 6.2.1
This class comprises instances of E92 Spacetime Volume that result from intersection of instances of E92 Spacetime Volume with an instance of E52 Time-Span. The identity of an instance of this class is determined by the identities of the constituing spacetime volume and the time-span.
This class can be used to define temporal snapshots at a particular time-span, such as the extent of the Roman Empire at 33 B.C., or the extent occupied by a museum object at rest in an exhibit. In particular, it can be used to define the spatial projection of a spacetime volume during a particular time-span, such as the maximal spatial extent of a flood at some particular hour, or all areas covered by the Poland within the 20th century AD