The fact that an actor is connected to the system
means that they supply information to the system, or obtain information from our
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system, or both. The type of information exchanged here, and who participates
in the exchange, is well known in this early project phase. Though you may be
frowning now, it is not a matter of saying how the exact protocol to the external
systems should look like. The information we look for is initially much more
abstract. What sort of information does the on-board computer get from the customer?
Right, card data or a PIN, for example.
We want to write this information down at this point, at which it isn ??™ t a matter
of achieving completeness. It ??™ s rather a matter of documenting the knowledge the
participants have gained so far and improving the understanding of the way our
system is embedded in its environment. During the subsequent steps within our
approach we will use this information to add details to our model and to further
complete it (see Section 2.4.1).
The system context model with its information fl ow essentially serves two goals:
1.
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