Geoscience Reference
In-Depth Information
Fig. 4
Topology of time
(NBN
2005
)
geometric temporal primitives can also be expressed in absolute terms, by the dis-
tance-method of the TM_Separation class (Fig.
3
). This class provides as well an
operation to calculate the duration of a period (NBN
2005
). Although the duration
of an instant is by default equal to zero, the ISO standard provides a calculation
operation for this (NBN
2005
).
The second category of temporal objects described by NBN EN ISO
19108:2005 (NBN
2005
) are topological primitives. These objects only pro-
vide information about connectivity and ordering in time, not about the tempo-
ral position (ISO 2002). In analogy to spatial topological primitives (ISO 2003),
TM_Node and TM_Edge represent 0D and 1D topological temporal primitives
respectively (Fig.
4
) (NBN
2005
). When the position of a node or edge in time
is known, the topological primitive can be associated to its geometric representa-
tion (NBN
2005
). In order to represent connectivity between different topologi-
cal primitives, each primitive should be part of a TM_TopologicalComplex (NBN
2005
). The order of topological primitives belonging to the same complex can be
derived through the TM_Order interface and its RelativePosition()-method. This
method will return, in this case, one of the temporal Allen relations of which four
are excluded: during, contains, overlaps and overlapped by.
3.2 Temporal Reference Systems
A temporal position is related to a temporal reference system to which the
value is measured. The NBN EN ISO 19108:2005 standard (NBN
2005
) speci-
