Ordering Events in Hierarchical Cyber-Physical Systems

Contact: Maaz Mashood Mohiuddin

Background:

Cyber-physical systems (CPSs) are physical processes that are monitored, coordinated or controlled by a computing and a communicating core. Examples of CPSs are smart-grids, autonomous cars, etc. These systems control the physical process using two types of software agents, namely controllers and process agents (PAs). The PAs measure the state of the process and send them as measurements to the controller. The controller uses these measurements to compute and issues setpoints that are implemented by PAs to achieve the desired control.

In order to ensure correct control, the software agents require a total order among the events in a CPS. The conventional approach to ordering messages uses the happens-before or causality relation introduced by Lamport in [1]. However, the causality relation was recently shown to be inadequate for CPSs. To address this issues, the intentionality relation was proposed in [2]. In addition to order events among each other, the intentionality relation also orders events according to the an abstraction of the state of the process.

The intentionality was only defined for CPSs with one logically-centralized controller and one or more PAs. Several CPS use a hierarchy of controllers to control the process. The goal of this project is to extend the intentionality relation to CPSs with a hierarchy of controllers.

Project Goals

  1. Understand the happens-before and the intentionality relation
  2. List the requirements for CPSs with hierarchy of controllers
  3. Define the extension to the intentionality relation
  4. Design a labeling scheme using the new relation

Student Profile:

  • Admitted or applying to EDIC
  • Strong fundamentals in set theory
  • Background in distributed algorithms

References

  1. Lamport, Leslie. “Time, clocks, and the ordering of events in a distributed system.” Communications of the ACM 21, no. 7 (1978): 558-565.
  2. Saab, Wajeb, Maaz Mohiuddin, Simon Bliudze, and Jean-Yves Le Boudec. “Ordering events based on intentionality in cyber-physical systems.” In Proceedings of the 9th ACM/IEEE International Conference on Cyber-Physical Systems, pp. 107-118. IEEE Press, 2018.

Supervisors: Maaz Mashood Mohiuddin