The class SpatiotemporalObject is defined as a subclass of both SpatialObject and TemporalObject. Consequently, a member of SpatiotemporalObject includes objects belonging to the following classes: GeometricObject, SpatialReferencing, TimeObject, and TemporalReferencing. Time may be specified as part of a coordinate (see below). Since geometry contains coordinates, time may be included directly in the geometry. This is practical where the geographic object occurs at a single point specified for example in terms of an (x,y,t) coordinate. Time may also be specified independently as a value for TimeObject. If the geographic object is an areal feature, then defining every point on a polygon's boundary with an (x,y,t) coordinate is inappropriate. Instead, (x,y) coordinates should be used and a value for TimeObject should be provided.
Geometry may include time in coordinate value, and a value for timeObject may be given as well. This is practical in two situations. In both cases, the timeObject value provides a duration during which the geographic object existed. In the first case, time values in the coordinates refer to specific times or dates during that duration when the geographic object was observed. Consider the duration of a bicycle trip with the route defined by an arc with (x,y,t) coordinates for the points on the arc. The values for the time coordinate refer to actual time.
In the second case, time values in the coordinates come from the class Interval; that is, they represent relative time, measured in seconds, minutes, hours, etc. are given. These interval values represent time from the start time, as specified in the value for the duration. Consider the bicycle trip again, but in this case the values for the time coordinate represent minutes and seconds relative to the beginning of the trip.