Geoscience Reference
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positioned inside. It is an
endurantist
vision. The second refers to a conception
denoted “4D” in which objects, events and processes define together hyperobjects.
This conception is compatible with a
perdurantist
vision. The consequence is that
there is no
variation
in time or space, it is integrated in the hyperobject (see
Figure 1.5).
1.2.2.
From change to objects' life
Research in the area of integration and formalization of time in information
systems are not new, and the 1990s mark the beginning of specific formalisms with
respect to the introduction of time into geographical information systems. If these
last 20 years have seen a good number of conceptual and operational formalization
developments, a true gap was observed between these advances in the field of
research and their integrations into geographical information systems [OSU 05].
These systems have been strongly modeled by the cartographic culture consisting of
presenting territories' states, the most up-to-date, and they still leave today to the
responsibility of users the care to generate evolution and change. This is done most
of the time by multiplying static layers for each date.
In recent years, these attempts were enhanced by reflections on the ontological
categories previously presented. Without making a detailed review of all the
formalizations developed, nor of the computer developments, for which readers
are referred to specialized analyzes [ABR 99, YUA 01, WOR 05, PLU 11], we
propose here to walk through the different stages of these developments. Indeed,
they raise interesting questions, some of them still remaining unanswered.
The model corresponding to cartographic use, consisting of giving an updated
status of a map, is the snapshot model. Change can then only be identified by
comparing two successive states of the map. That is often still the used model.
However, the first foundations of the issues associated with the introduction of time
in order to identify change have been posed since 1988 by Langran and Chrisman
[LAN 88]. They already pointed to the fact that a representation of the dynamics by
simple superposition of dated layers (“stamped”) represents only an accumulation of
states where time only exists through the interpretation of the user. They proposed a
“Space-Time composite” model based on the differentiation between the status of
the map and those of the objects (versions). That way they introduced a
differentiation between the changes at the object level (mutation) and the result of
these changes at the map level (event) (Figure 1.6). The data model that they
propose is change-based in the case of a field-oriented approach. If the field's
elements are pixels, each pixel is described by the sequence of its states. In the case
of a non-regular partition of space for example, polygons of land use, these are
