6.1.1 Global data bases 
In this context we mean with global data base a permanent 
(but still dynamic) data base in an organisation we are 
dealing with. Taking aerial triangulation as an example, 
essential information includes calibration data of camera 
and files of control point data. 
Complete integration between the global data base system 
and the application software might be hindered by technical 
and operational obstacles, especially when the integration 
is desired to be done for a portable application software. 
Firstly, the data input/output interfaces of the 
application software has to be adapted to the corresponding 
ones of the data base system. In worst case, if the data 
base schema of the pertinent data does not follow the 
structure assumed in the program, massive reprogramming is 
required to convert the data to the required format. If 
some commercial data base system is used, difficulties are 
even likely, as observed by Elassal (1985). This is due to 
the fact that commercial data base systems are usually not 
well suited for dealing with numerical data. Question of 
efficiency is also important, especially in those parts of 
the application program where data base is used 
extensively. If the data base system does not support 
desired access methods well, then efficiency is poor. This 
can be due to required conversions or complicated access 
paths. 
Secondly, the operational aspects have to be solved. If we 
work within a multi-person organisation, it is likely that 
somebody wants to alter data in the data base while an 
application program is running. If not properly treated, 
these alterations can have catastrophical consequences on 
the integrity of the internal data of the program. 
How should we solve these problems? A simple solution is to 
restrict the access of the application program to the 
global data base. This can be achieved by using front/back 
ends that load the required data from the global data base 
to an independent run-time data base. At the end of the 
session reverse operations are performed. 
This approach offers some obvious advantages: 
- the application data base can be designed to fullfil 
all the special requirements of the application 
- the application program is working with a static 
environment and consistency problems are avoided on 
application level 
- application program is well portable, only the 
front/back-end modules have to be adapted for the 
environment 
However, there are also disadvantages. Firstly, the 
consistency problem now occurs between the global data base 
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