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70 Chapter 2

Exercise 2.4 Binary counter

The following (binary) counter is to be modeled as a Petri net. The marking of a place represents a binary value (1 or 0). The combination of the markings of these places represents the natural number that is dis-played by the counter. For example, the binary number 101, that is, 5, marks two places corresponding to a “1” (i.e., the places 2² and 2°) and one place corresponding to a “0” (i.e., the place 2¹).

Make a model of a counter able to count from 0 to 7.

Exercises High-Level Petri Nets

Exercise 2.5 Driving school

A driving school is trymg to set up an information system to track the progress of the students’ training and the deployment of instructors. As a starting point for a formal process model the following description can be used.

New students register with the driving school. A registered student takes one or morę driving lessons folłowed by an examination. Each driving lesson has a beginning and an end. Instructors give driving lessons. The driving school has five instructors. Each driving lesson is fol-lowed by either another lesson or an examination. The examination has a beginning and an end and is supervised by a driving examiner. In total there are ten driving examiners. For the outcome of an examination there are three possibilities:

1.    The student passes and leaves the driving school.

2.    The student fails and takes additional lessons in order to try again.

3.    The student fails and gives up.

(a)    Model the driving school in terms of a classical Petri net.

(b)    Use a colored Petri net to model that one takes ten lessons before taking the exam and people will drop out if they fail three times.

(c)    Add time to model that a lesson takes one hour and an exam thirty minutes.

Exercise 2.6 Bicycle factory

A factory produces bicycles (just one type). The Bill Of Materials (BOM) is given in figurę 2.29.