The user may define subclasses of this class.
A graph is a set of instances of the ConnectedTo relationship. It establishes connections between pairs of geographic objects. A given geographic object may appear any number of times in the connections attribute. Two subclasses of Graph are defined in the standard schema: AcyclicNetwork and SingleLineNetwork.
The term graph does not necessarily imply that the related geographic objects are contiguous in space or time. However, the term network typically does imply such contiguity. Use of AcyclicNetwork, SingleLineNetwork, or any user defined network classes should take this into account.
For each instance of ConnectedTo, a connection direction may be provided through the enumeration ConnectionDirection.