Exercises

Exercises 3.1 to 3.6 are more instructive and interesting if the FSP models are developed using the analyzer tool LTSA.

• 3.1 Show that S1 and S2 describe the same behavior:

   P = (a->b->P). Q = (c->b->Q). ||S1 = (P||Q). S2 =(a->c->b->S2| c->a->b->S2).

• 3.2 ELEMENT=(up->down->ELEMENT) accepts an up action and then a down action. Using parallel composition and the ELEMENT process describe a model that can accept up to four up actions before a down action. Draw a structure diagram for your solution.

• 3.3 Extend the model of the client – server system described in section 3.1.4 such that more than one client can use the server.

• 3.4 Modify the model of the client – server system in exercise 3.3 such that the call may terminate with a timeout action rather than a response from the server. What happens to the server in this situation?

• 3.5 A roller-coaster control system only permits its car to depart when it is full. Passengers arriving at the departure platform are registered with the roller-coaster controller by a turnstile. The controller signals the car to depart when there are enough passengers on the platform to fill the car to its maximum capacity of M passengers. The car goes around the roller-coaster track and then waits for another M passengers. A maximum of M passengers may occupy the platform. Ignore the synchronization detail of passengers embarking from the platform and car departure. The roller coaster consists of three processes: TURNSTILE, CONTROL and CAR. TURNSTILE and CONTROL interact by the shared action passenger indicating an arrival and CONTROL and CAR interact by the shared action depart signaling car departure. Draw the structure diagram for the system and provide FSP descriptions for each process and the overall composition.

• 3.6 A museum allows visitors to enter through the east entrance and leave through its west exit. Arrivals and departures are signaled to the museum controller by the turnstiles at the entrance and exit. At opening time, the museum director signals the controller that the museum is open and then the controller permits both arrivals and departures. At closing time, the director signals that the museum is closed, at which point only departures are permitted by the controller. Given that it consists of the four processes EAST, WEST, CONTROL and DIRECTOR, draw the structure diagram for the museum. Now provide an FSP description for each of the processes and the overall composition.

• 3.7 Modify the example Java program of section 3.2.2 such that it consists of three rotating displays.