February 25 – 28 , 2018, Dagstuhl Seminar 18092

The Logical Execution Time Paradigm: New Perspectives for Multicore Systems


Rolf Ernst (TU Braunschweig, DE)
Stefan Kuntz (Continental Automotive GmbH – Regensburg, DE)
Sophie Quinton (INRIA – Grenoble, FR)
Martin Simons (Daimler AG – Böblingen, DE)

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The Logical Execution Time (LET) abstraction, which was originally introduced as a real-time programming paradigm, has gained traction recently in the automotive industry with the shift to multicore architectures. The objective of this Dagstuhl Seminar is to investigate new opportunities and challenges raised by the use of LET as a basis for implementing parallel execution of control software.

LET abstracts from the actual timing behavior of real-time tasks on the physical platform: Independent of when a task executes, the time interval between its reading input and writing output is fixed by the LET. This introduces a separation between functionality on the one hand, and mapping and scheduling on the other hand. It also provides a clean interface between the timing model used by the control engineer and that of the software engineer.

The LET paradigm was considered until recently by the automotive industry as not efficient enough in terms of buffer space and timing performance. The shift to embedded multicore processors has represented a game changer: The design and verification of multicore systems is a challenging area of research that is still very much in progress. Predictability clearly is a crucial issue which cannot be tackled without changes in the design process. Several OEMs and suppliers have come to the conclusion that LET might be a key enabler and a standardization effort is already under way in the automotive community to integrate LET into AUTOSAR.

The seminar will bring together researchers and practitioners from different backgrounds to discuss and sketch solutions to the problems raised by the use of LET in multicore systems, with a focus on the automotive domain. Specific questions include:

  • LET was designed as a programming paradigm but is now being used as a mechanism for predictable communication. How can the principles of LET be adapted accordingly? How should LET values be chosen?
  • LETs act as deadlines for tasks, which means that they must be dimensioned for the worst-case response time of tasks. This may be too inefficient in practice. Alternatives exist where a bounded number of deadline misses may be tolerated. How should LET exceptions (violations of the specified LET) be handled then? How can deadline miss patterns which still guarantee functional correctness (e.g., system stability) be established?
  • How should the LET constructs be integrated into AUTOSAR? More generally, how should the design and verification process in the automotive industry be modified to integrate the LET paradigm?
  • How does the use of the LET paradigm for multicore systems fit into the more general context of achieving predictability of multicore systems?

This seminar will provide a unique opportunity for participants from the automotive industry to get feedback from academia on their effort to adopt the LET paradigm. On the other hand, it will allow other participants to confront their own models and/or solutions with industrial reality and identify new research challenges. This seminar will furthermore bring together research communities which do not so often interact with each other, e.g. the synchronous, control and real-time communities. One expected outcome of this seminar is a joint statement in the Dagstuhl Report to be used from then on as a reference document on the use of LET in the automotive industry.

  Creative Commons BY 3.0 DE
  Rolf Ernst, Stefan Kuntz, Sophie Quinton, Martin Simons, and Hermann von Hasseln


  • Modelling / Simulation
  • Optimization / Scheduling
  • Semantics / Formal Methods


  • Logical execution time
  • Real-time systems
  • Control
  • Multicore architectures

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