Tutorial series 2021

The IEEE CSS TC DES is organizing a Virtual Lightning Tutorial Series on Discrete Event Systems throughout 2021 to enhance communications in our community during the current Covid-19 pandemic. 

Recordings and slides of past talks are available here  (register to obtain password)

Time & Date:

The tutorials take place virtually via Zoom on the 3rd Thursday of each month in 2021 (except August) at 13:00 UTC (Paris 14:00, New York City 9:00, Beijing 21:00). Please see the detailed schedule below.

Scope:

In order to include members of our community on all levels (ranging from phd-students, to post-docs, to junior and senior faculty members) we have decided on the format of “lightning tutorials”, followed by a virtual coffee break organized via break-out rooms randomly assigning 5-6 people to a room for more informal chatting. Lightning tutorials are rather short (≈ 40 minutes) and are intended to introduce a fundamental or emerging topic/sub-field of DES research to a broad audience. They can be thought of as an introduction to a review paper or a book chapter, introducing the particular topic/sub-field, why it is worth studying (either from a theoretical or a practical perspective), its main insights (what is known/what is unknown) and maybe a list of influential papers in this field.

Registration:

Registration is free. For security reasons we require pre-registration. Participants will receive log-in details to the virtual zoom meeting after registration.

Please register here!

Schedule:

State Estimation and Event Inference in DES: Implications to Detectability, Diagnosability and Opacity

  • Speaker: Christoforos Hadjicostis

  • Date: January 21

  • Abstract: We discuss recursive algorithms for state estimation and event inference, both of which are key tasks for monitoring and control of discrete event systems. In particular, we discuss algorithms for current-, initial-, and delayed-state estimation. We also discuss implications to various pertinent properties of interest, such as detectability (i.e., the ability to determine the exact system state after a finite number of events), diagnosability (i.e., the ability to detect within finite time the occurrence/type of a fault), and opacity (i.e., the guarantee that outsiders will never be able to infer that the system state lies within a set of certain secret/critical states). The talk also briefly discusses the extension of state estimation and event inference methodologies in emerging decentralized/distributed observation settings.

Discreet Event Systems: Opacity and Its Enforcement

  • Speaker: Stephane Lafortune

  • Date: February 18

  • Abstract: Opacity is an information-flow property used in privacy and security applications. A dynamic system is opaque if an external observer that knows the system model and makes online observations of its behavior is not able to detect with certainty some "secret" information about the system. We discuss various notions of opacity and their verification in the context of discrete event systems modeled by automata or transition systems: current-state opacity, initial-state opacity, and K-step opacity. Then we consider how to enforce opacity for systems that are not opaque. We focus on opacity enforcement using obfuscation, when an external interface edits the outputs of the system in order to confuse the observer. We present solution methodologies for different variations of this problem. We conclude with illustrative examples of opacity in the context of location privacy in location-based services.                                  

Abstractions: A Bridge Between Continuous Dynamics and Discrete Event Systems

  • Speaker: Necmiye Ozay

  • Date: March 18

  • Abstract: In this talk, we will give an overview of finite abstractions, which are graph-based representations for continuous-state control systems. If these finite abstractions are constructed properly, they can be used to design controllers using techniques from discrete event systems or reactive synthesis in a way that the designed controller can be implemented on the underlying continuous control system (namely, the concrete system) and provide guarantees on the closed-loop behavior. In order to lead to a correct-by-construction design, the abstract system should satisfy a certain relation with the concrete system. We will introduce several such relations including, (bi)simulation relations, over-approximations, feedback refinement relations, and discuss what type of properties are preserved under these relations. Finally, we will discuss various ways of constructing these abstractions, e.g., based on gridding or partitioning the state space, for different classes of systems, e.g., discrete-time or continuous-time. Several examples will be used throughout to demonstrate these techniques in action. The talk will conclude with a summary of more recent results and a discussion on several research directions.                                       

Distributed Synthesis

  • Speaker: Stavros Tripakis

  • Date: April 22

  • Abstract: I will give a brief tutorial of synthesis in a distributed setting, where the goal is to automatically synthesize, if they exist, a set of distributed observers or controllers which together achieve a specific goal. Rather than giving an exhaustive survey I will focus on specific aspects of the problem. In particular, my talk will be structured in two parts. In the first part I discuss theoretical aspects, specifically decidability and undecidability. In the second part I discuss distributed synthesis in practice, specifically, automatically synthesizing protocols such as the Alternating Bit Protocol using a combination of example scenarios and formal specifications as user inputs.                                         

A Survey on Petri Nets Models for Logistics and Transportation Systems

  • Speaker: Mariagrazia Dotoli

  • Date: May 20

  • Abstract: Logistics and transportation systems are man-made systems that are well suited for modeling in a discrete event system framework and particularly by Petri Nets (PNs), due to their different characteristics: distributed, parallel, deterministic, stochastic, discrete, and continuous. The paper presents a survey on the various Petri nets modeling frameworks proposed in the related literature for logistics and transportation systems, with applications to modeling, simulation, analysis, optimization and control. In particular, we focus on papers dealing with freight transportation and outline and classify the related works conducted using PNs as regards the proposed framework and addressed problems. We also debate the approaches viability, discussing contributions and limitations, and identify future research potentials.

From Perturbation Analysis of DEDS to a General Optimization Theory in the AI Era

  • Speaker: Xiren Cao

  • Date: June 17

  • Abstract: Information systems have many special features such as large scale, big data, uncertainty, dynamic structure, and no mathematical models or unknown parameters. The traditional model-based analytical approach may not be suitable for the optimization of such systems. Learning-based approach must be used. “Learning” refers to the process of predicting the behavior of other related systems by analyzing a sample path of a given system. Perturbation analysis (PA) is one of the early development in this direction, which provides the performance derivatives based on a single sample path. Relative optimization can be viewed as an extension of PA from infinitesimal changes to finite ones. Its essential idea is comparing of the performance measures under two different policies based on analyzing the system under one policy. The philosophy behind this approach, the main concepts and results, its difference with dynamic programming, and its relation with reinforcement learning, etc., are discussed. Examples show that this learning-based approach solves some long-standing issues in optimization and therefore pushes forward the development of optimization theory.                              

Partially Observed Discrete Event Systems: from Estimation to Cyber-Security

  • Speaker: Alessandro Giua

  • Date: July 22

  • Abstract: The abstract of this talk will be avaliable soon                                         

On Modular and Compositional Approaches to Compute Supervisors

  • Speaker: Martin Fabian

  • Date: September 16

  • Abstract: The abstract of this talk will be avaliable soon                                         

Supervisory Control of Non-Terminating Processes — a Concise Introduction

  • Speaker: Thomas Moor

  • Date: October 21

  • Abstract: The abstract of this talk will be avaliable soon                                         

Synthesis-Based Engineering of Supervisory Controllers – From Specification to Implementation

  • Speaker: Joanna (Asia) van de Mortel – Fronczak

  • Date: November 18

  • Abstract: In cyber-physical systems, safety and availability are of utmost importance. To satisfy requirements on safety and availability, suitable supervisory controllers need to be employed. Supervisory control theory provides a foundation on which a model-based engineering method has been developed, providing guarantees on the correctness of resulting supervisory controllers with respect to the defined requirements. In this lecture, an overview will be given of the recent research projects at Eindhoven University of Technology aiming at the development of extensions to this method, and of supporting tools, giving rise to an integrated approach to the design of supervisory controllers for complex real-life systems. This includes a mathematically underpinned, straightforward and error-free path to implementation of the designed controllers. The research projects are related to the partnership with Rijkswaterstaat which is a part of the Dutch Ministry of Infrastructure and Water Management.

Event-Driven Receding Horizon Control for Complex Problems in Network Systems

  • Speaker: Christos Cassandras

  • Date: December 9

  • Abstract: The abstract of this talk will be avaliable soon