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of each of the models quantitatively. The number of classes indicates clearly that
the model proposed by Michalak ( 2005 ) which includes both topology and geome-
try, is more complicated (5 vs. 3/2). However, this disadvantage is counterbalanced
by the advantages. The latter model enables the use of both, eras with and with-
out precisely known boundaries. The model proposed by Cox and Richard ( 2005 )
can be placed in between the NBN EN ISO 19108:2005 (NBN 2005 ) version and
the variant of Michalak ( 2005 ). This model allows distinguishing boundaries from
their eras, but at the other hand, the temporal position of these boundaries still
requires a precisely known date. This induces that the ISO model for the tempo-
ral ordinal reference system is not complete enough to be suitable for the defini-
tion of the archaeological time scale. The variant of Cox and Richard ( 2005 ) is
more extensive, but does still need precisely known dates. The variant of Michalak
( 2005 ) is basically topological, and thus, focusses on ordering rather than on the
exact dates. However, the model permits the geometric positioning of the tempo-
ral era boundaries. These advantages lead to the conclusion that Michalak's model
( 2005 ) which combines topology and geometry is the most sufficient one for use
in archaeology.
6 Conclusions
The suitability of the NBN EN ISO 19108:2005 (NBN 2005 ) standard on temporal
information for archaeological data is assessed in this chapter. The first part of the
applicability analysis focused on six temporal categories, which are frequently
assigned to archaeological objects. As discussed above, most of these categories
can be given a formal description conform to the standard, and this as well for the
single excavation objects as for the complete site. Excavation and database times
can be specified as TM_Instant for the objects and as TM_Period for the complete
site. In both cases, the temporal position given as Date or DateTime. Both, the
site phase time and stratigraphic time of excavation objects, can be described as
TM_Edge and grouped into a TM_TopologicalComplex, which can be assigned
to the respective properties of the archaeological site. The structuring of strati-
graphic times into topological complexes allows identifying the (spatio-tempo-
ral) relationships used in the Harris matrix, which is a main and one of the first
temporal analysis tools. Both the site phase and stratigraphic time can have 3D
spatial extents which bound the objects with different values. The archaeological
time can be specified as a TM_Instant or TM_Period for the excavation objects
and site respectively. Their temporal position is referenced to a temporal ordinal
reference system. For the sixth category, the absolute time, the description as a
TM_Instant (for the site's objects) or TM_Period (for the site) with data type Date
is chosen. Concerning this last property, a small remark has to be made. Absolute
dates are not that fixed as the name leads one to suspect. Absolute dates coming
from scientific methods like C14-dating are mostly characterized as a date range
or by probabilities. Therefore, the suggestion is made to split the category into a
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