ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS", Bangkok, May 23-25, 2001
331
3.2 THE IMPLEMENTATION OF THE COMPOSITE
TEMPORAL DATA MODEL
The implement of the composite temporal data model (tab.2) is
described. 1. Open initial cadastral database, exhibit the current
cadastral state as initial cadastral state in that it is accessed
more frequently than any other historical states in general. 2.
Open time-privilege database. 3.Input given time, users’ login
IDs and their passwords. 4. if OK, retrieve the backup file—the
closest to given time, as initial cadastral file; otherwise, Close
and Return to the current state; 5. Open action database and
restore changed land-parcels according to action records until
the current state fully accords with the state at given time. Thus,
historical state of given time is restored completely. Moreover,
table.2 the retrieval of historical states flow chart
the time of restoring historical state is quite short. The reasons
are IThe cadastral map and the base map are stored into
separate layers. While only cadastral data, which are quite fewer
than other data, are processed in historical data management,; 2.
What’s more, only changed cadastral data —‘delta variables’,
which record the differences between the previous states and
the current state, are recorded into the actions database; 3.
Because snapshots about cadastral maps of different time points
are stored in initial cadastral files, the backup cadastral snapshot
- the closest to given time point can be quickly retrieved as
initial cadastral state, on the basis of the initial cadastral state,
the changed spatial units—land-parcels are quickly restored
according to action records in action database.
