Geoscience Reference
In-Depth Information
Since the NBN EN ISO 19108:2005 (NBN
2005
) mentions archaeology explic-
itly as one of the applications where an ordinal temporal reference system is more
appropriate than another temporal reference system (p. 20), this part of the stand-
ard is applied to the archaeological time scale. Multiple archaeological time scales
exist based on different spatial or cultural regions. In this chapter, the archaeologi-
cal time scale for Western Europe is used. Although different versions occur, the
main periods and subperiods are largely accepted. However, begin and end dates
vary according to the spatial location and/or are not exactly known. In the exam-
ple used in this chapter, the choice is made to use dates described by the Flemish
Heritage Agency (Onroerend Erfgoed
2012
) and about which general acceptance
as rough dates for the Flemish region exists.
Similar research is done for the geological time scale by Michalak (
2005
) and
Cox and Richard (
2005
). Although both of them presented almost simultane-
ously a temporal model for the geological time based on ISO 19108, two differ-
ent results were obtained. Michalak (
2005
) adapted the structure of the Temporal
Ordinal Reference System (NBN
2005
) with topological elements. Cox and
Richard (
2005
), on the other hand, developed the system with geometric elements.
In this research, the ISO version of the temporal ordinal reference system as well
as the adapted versions of Michalak (
2005
) and Cox and Richard (
2005
) will be
applied to the West European archaeological time scale. To clarify the differences
between the three variants, only a part of the archaeological time scale is used: the
Roman time including three subperiods (Early, Mid and Late Roman time) and the
Middle Ages. The prefix 'TM_' is used where classes of the original standard are
used. After the comparison of the pros and cons of each of the models, a proposal
will be given about the most sufficient system for the (West European) archaeo-
logical time scale.
5 Results and Discussion
5.1 Six Temporal Categories
The first temporal category that can be assigned to an excavation object is the
excavation time. This is the date an object is excavated or found. Since this date
can be identified to the level of day, month or year or at best to the hour (min-
ute, second) level, for the representation a geometric primitive is selected. It
is assumed here and by Katsianis et al. (
2008
) that the value for this date is 0D
and thus a TM_Instant. In this case, the TM_Calendar, possibly supplemented by
the TM_Clock temporal reference system is chosen. The position of the instant
is, thus, provided by 'date8601:Date' for dates down to the level of a day or
'dateTime8601:DateTime' for more specific dates which include hour, minutes
and/or seconds. These two options use the default temporal reference system:
Gregorian calendar and UTC, as described in ISO 8601 (NBN
2005
, p. 21). With
