Specification of Reactive Hardware/Software Systems - Electronic ...

40 Concepts for Analysis, Specification and Design
Stations contain numerous sensors, actuators and system functions controlled by a
central control station. The central control station is realised with PLC technology.
Another part of the functionality is realised mechanically. Figure 3.3 shows that all
stations are connected to the central controller by dedicated connection channels. In
practice these connections are realised by many cables each containing numerous wires.
The actual situation is that new machines are installed and tested completely in the
machine production facility. Subsequently all cables are disconnected and all stations
packed and shipped to a customer somewhere in the world. At the customers site all
parts are reconnected and the machine has to be tested again.
3.6.2 Requirements for a New Type of Mailing Machine
Of course there are many new requirements for the successor of the existing Mailing
Machines. In this brief introduction we mention only the major requirements.
1. To remain competitive it must be possible to cut costs substantially. The new machine
must therefore be realised as a collection of more autonomous stations that
can be installed relative simple by a so-called plug-and-play concept. It must be
possible to build and test the stations independently. The cost of building, connecting,
and testing a complete line first in the factory and second at the customers site
can be diminished dramatically by the plug-and-play approach. In addition this
approach leads to more flexibility. A customer can extend his production line with
additional stations simply by insertion of additional stations. With the current machine
concept this would require reprogramming and substantial modifications of
the machine.
2. The mailing market wants to cut costs by sending advertising mail in a personalised
form in the future. Nowadays many mailing jobs come down to making
identical product packets for the whole collection of mailing addresses. In case
of personalising packets, their contents can differ. Only items that are useful for
a particular receiver should be inserted into the packet for that receiver. This
requirement makes a Mailing Machine substantially more complex. When the
stations must perform different actions at different times they must have access to
information about the packets to be put together.
3.6.3 Conceptual Solution
Many designs and product ideas in general start from an initial idea or technology that
can be used to create a solution for the customer needs. We call such a basic idea a
conceptual solution. Alternative conceptual solutions are often evaluated in a so-called
feasibility study. It does not make sense to invest a lot of effort in a precise specification
when the conceptual solution is not yet determined. A good conceptual solution gives
confidence in the value of an investment in a specification, and enables risks and costs
to be assessed.
A conceptual solution will often impose a physical or logical structure on a system.