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

10.5 Example: The Elevator Problem 321
Overweight
Sensor 0
Floor
Sensors
0
Elevator
Motor
Control
Module 0
Elevators
Control
Module
Elevator
Motor 0
Operator
Audible
Alarm 0
Doors 0
Elevator
Cage
Control
Module 0
Floor
Passenger
Interface
Module 0
...
Floor
Passenger
0
Elevator
Passenger
0
Figure 10.2: Architecture Structure Diagram of the Elevator Problem
To be able to implement the POOSL specification shown in Figure 10.1, it has to be
decided on which physical modules the different process instances (and possibly the
different cluster instances) will be mapped. Further, a mapping of logical communication
channels onto physical ones has to be decided upon. In this example the latter
mapping easily follows from the former one.
If the required mappings have been defined, the structure defined in Architecture Structure
as well as the chosen mappings are formalised by transforming the POOSL specification.
The transformed specification is such that its structure precisely matches the
structure of the Architecture Structure Diagram.
There are quite a few possibilities to map the different instances of Figure 10.1 onto
the physical modules of Figure 10.2. To make a proper choice, it would be necessary
to evaluate the different alternatives by comparing them with respect to for example
performance, feasibility and cost. Since the different architecture structures are formalised
in POOSL, such a comparison could in principle be supported by automated
tools [GV95]. The development of such tools will be subject of future research.
In this example we will choose a fixed mapping and show the result of the applications
of the required transformations. The mapping is as follows:
One OverweightSensorImage and one ElevatorMotorImage is mapped onto each
ElevatorMotorControlModule.