Geoscience Reference
In-Depth Information
Fig. 10
Model for temporal reference systems adapted from ISO 19108 by Cox and Richard
(
2005
)
data type, since they all consider the temporal position as fixed. The use of
TM_OrdinalPosition to specify the boundary of a temporal era in a temporal ordi-
nal reference system could lead to confusion.
Michalak (
2005
) introduced around the same time another variant of the NBN
EN ISO 19108:2005 temporal ordinal reference system, shown in Fig.
12
. Before
presenting his adapted version of the model, Michalak (
2005
) first outlined the
shortcomings of the model presented in the ISO standard (Fig.
5
). In the standard,
no indication is made about the inheritance of the class TM_OrdinalEra (Michalak
2005
, p. 868). However, Michalak (
2005
, p. 868) found some arguments demon-
strating that TM_OrdinalEra implicitly inherits from TM_GeometricPrimitve:
The relationship with TM_Separation. This interface has operations for the calcula-
tion of distance and length and can, therefore, only handle geometric temporal objects.
The begin and end attributes belong to the geometric domain, since they repre-
sent temporal positions.
Another issue is reported by Michalak (
2005
): the multiplicity '0...1' for the
attributes 'begin' and 'end' can cause problems for the performance of the TM_
Separation interface. It is impossible to use the operations length() or duration()
when no values are given for the attributes.
