Discrete Event Systems (HS 2016)
Over the past few decades the rapid evolution of computing, communication, and information technologies has brought about the proliferation of new dynamic systems. A significant part of activity in these systems is governed by operational rules designed by humans. The dynamics of these systems are characterized by asynchronous occurrences of discrete events, some controlled (e.g. hitting a keyboard key, sending a message), some not (e.g. spontaneous failure, packet loss).
The mathematical arsenal centered around differential equations that has been employed in systems engineering to model and study processes governed by the laws of nature is often inadequate or inappropriate for discrete event systems. The challenge is to develop new modeling frameworks, analysis techniques, design tools, testing methods, and optimization processes for this new generation of systems.
In this lecture we give an introduction to discrete event systems. We start out the course by exploring the limits of what is computable and what is not. In doing so, we will consider three distinct models of computation which are often used to model discrete event systems: finite automata, push-down automata and Turing machines (ranked in terms of expressiveness power). In the second part of the course we analyze discrete event systems. We first examine discrete event systems from an average-case perspective: we model discrete events as stochastic processes, and then apply continuous time markov chains and queueing theory for an understanding of the typical behavior of a system. Then we analyze discrete event systems from a worst-case perspective using the theory of online algorithms and adversarial queueing. In the last part of the course we introduce methods that allow to formally verify certain properties of Finite Automata and Petri Nets. These are some typical analysis questions we will look at: Do two given systems behave the same? Does a given system behave as intended? Does the system eventually enter a dangerous state?
Course language: English and German
Regarding the second part of the course (given by Prof. Wattenhofer), the following parts of the lecture notes are relevant for the exam: Chapter 5 and Sections 6.1-6.6 from Chapter 6. An exception is Section 6.5, where we only assume knowledge of the parts covered in the lecture, i.e., Definition 6.19 and Lemma 6.20, and related remarks. While the exam questions can be answered without specific knowledge of Sections 6.7-6.12 and the remainder of Section 6.5, we recommend those parts as training material.
At the beginning of every lecture week, we will publish a new exercise sheet here. This exercise sheet is intended to be solved during the exercise session on Thursday where two tutors will be available to assist you and to answer potential questions. The exercises often require information from the lecture notes, so please make sure that you have them available in some way.
You can hand in your solutions for correction after the exercise session on a voluntary basis. But this is not mandatory or required to be admitted to the exam.
Last sessions schedules
The last two lectures by Prof. Thiele will be on the 8th and 15th of December. Exercises will follow the lecture, as usual. For the last week of the semester (Dec.22) there will be no lecture but the last exercise session, in the lecture slot (1pm)!
In the last slot (3-5pm), there will be a revision session with the teaching assistants of the three parts of the lecture, so that you can ask questions on any point covered during the course. You will also go through last year exam.
Please keep in mind that the content of the lecture has been updated a few times in recent years! Thus, some of the material from the old exams might no longer be covered in the current lecture and additional material has been added.