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3.3 DATA SECURITY 
From the legal perspective, cadastral data can not be modified 
without permission. However, static historical states (such as 
snapshots) can be changed by editing or other methods. In the 
composite model, all historical data except initial states are 
dynamically except initial states are dynamically created in 
memory. Besides, users login IDs and their passwords can be 
set in historical data tables as other attribute tables of the 
relational database. In other words, when the initial cadastral 
state is reinstated to the state at the time given, only authorized 
users can access the current cadastral state. Otherwise, users 
can not trace back previous states at all, even less change 
cadastral data. If initial cadastral data are modified without 
system access, the retrievable chain is broken and all updated 
data are not stored into the database. 
4. SOLUTIONS 
The described above indicate the importance of the 
spatio-temporal data model in CIS. Almost every step of 
cadastral management concerns the temporal problem. The 
intention of the work described here has not been to develop a 
full functional GIS platform, but to design and implement a 
temporal data model on the basis of the current GIS platforms to 
support spatial and temporal applications. Taking an example of 
Cadastral Information System for Wenzhou city, the composition 
temporal data model, which has little redundant storage, quick 
historical retrieval and security of storing data, can meet the 
practical need of temporal Cadastral Information System. 
In this chapter the composition temporal data model 
focuses on the management of vector spatio-temporal data and 
is adaptable to the situation where changes are frequent or there 
exist many asynchronous changing data items and applications 
concentrated on micro contacts and micro status discovery at a 
moment, future research will be the further development of 
raster types and the studying of macro changes about 
geographical phenomena. 
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