A Toy Problem

Here a small example (cf. figure 3.1, 3.2).

Figure 3.1: Example Problem: Open door with keypad

Figure 3.2: Example Problem: Open the electronically controlled door

We take as a toy problem an electronically controlled door. To open the door you have to key in a password. We assume here that this password consists of a string with the three letters ABA.

As described in the preceding chapter The Engineering Framework our first intention is the modeling of the expected behavior of the intended machine (M), which appears here as a door which will only open if you enter the right password ABA. To keep the example simple we will only model the expected behavior of the intended machine leaving aside the necessary behavior of the human person (H) and the environment (E).

The expected behavior of the machine M can be described by the machine interface (MI). The machine can receive input by the user as keyed in symbols and the machine can respond either by staying in an input receiving attitude or by actively open the door.

One can model such a behavior with the formalisms of automata theory combined with graph theory.