and the application data base. For example, if a point
identifier is updated in the global data base after the
loading of the application data base, the two data bases
are inconsistent, and the application software does not use
up-to-date information. A general solution would be to
integrate the application program functionally with the
organisational environment. Complexity of the system would
be increased tremendously, however. It would be almost
impossible to design such an application program to be
portable.
The front/back-end modules have to be tailored for each
organisation. This is an disadvantage. However, the clarity
of the solution is considered to pay off this extra work.
6.1.2 Implementation of the application (run-time) data
base
What kind of technique and tools should we use in
implementing the application data base when a high priority
is given for the portability? Especially, should we use
ready-made, commercial data base systems, or should we
Program the application data base starting from scratch?
For the decision, we have to analyse the common properties
of the commercial data base systems and the needs of the
application.
Flexibility: The commercially distributed systems are
flexible. They have been designed to be adaptable to a wide
range of applications. On the other hand, they are often
massive pieces of software. In addition, distribution is
limited by the licensing mechanism.
Needs of the application program: Needs, concerning the
data base, are static. The data types and the access
methods required will only be changed when the program is
modified by programming effort. According to the experience
of the author, only few access types are required. Thus,
from the technical point of view, there is no urgent need
for using commercial data base systems. Taking the
licensing costs, it becomes even more obvious that
commercial data base systems are usually not the best
solution.
What kind of programming style is suitable for hard-coded
implementations? One possibility is to use data arrays or
variables to store the information. This is no solution if
one does not structure the data such that the data base can
be distinguished from the rest of the program. In other
words, for the sake of program clarity, it is mandatory to
structure the program and separate different logical
components. Data base is one of the concepts that can be
used in this work.
As stated earlier, for a data base we have to define the
data entities and access methods. Those can be implemented
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