Flexible reliable timing constraints
Project no: 9905-1
Gerhard Fohler
Mälardalen University, Computer Engineering Department, MRTC
Application, support letter 1 from Mecel AB,
support letter 2 from University of Massachusetts, K. Ramamritham.
Comments by evaluator 1, evaluator 2, ARTES board.
Updated application.
Support: 1 PhD student for 2 years decided 99-08-26.
Start 2000-02-01 with Damir Isovic as PhD student.
Reports: First-year-report 01-07-10

Industry contacts

Lars Magnusson
Mecel AB
Project 1: A tool environment for the development of embedded systems
Project 2: Identification of Complexity-Reduction Techniques for Optimal Scheduling in Embedded Distributed Real-Time Systems
Project 3: Hierarchical Design and Analysis of Timed Systems
Project 4: Flexible reliable timing constraints
Project 5: RATAD, Reliability And Timing Analysis of Distributed systems
Project 6: Extension of Project “Flexible Reliable Timing Constraints”
Krithi Ramamritham
University of Massachsetts Amherst
Lederie Graduate Research Center
Project: Flexible Reliable Timing Constraints


Predictability and flexibility have often been considered as contradicting requirements, in particular from the scheduling perspective. This strong exclusion, however, holds only for predictability on a very detailed level, which is not demanded in most scenarios. Our research identifies appropriate levels of predictability, extends algorithms and architectures to combine static and dynamic components, and enables designers to combine predictability and flexibility.

Real-time systems need to be reliable in order to be applicable in real-world environment. Our approach to reliability follows the lines of timeliness: Instead of providing for static solutions only, we provide for adaptive fault tolerance and self-evolving systems. Issues include scheduling, dynamic reconfigurations of hardware structures, and reliability measures.

In this project, we develop methods for the derivation, specification, and run-time execution of activities with timing constraints, which exploit inherent flexibility in temporal demands, e.g., on application level, instead of over constraining specifications. We propose to use flexible timing constraints, which express feasibility information of activities rather than numbers demanded by common system models and scheduling algorithms. These will be scheduled by novel offline algorithms, which are capable of exploiting the expressed flexibility, while maintaining reliability requirements.


Ph D student Damir Isovic has finished his licentiate thesis entitled “Handling Sporadic Tasks in Real- Time Systems – Combined Offline and Online Approach”. The thesis has been presented on June 8th, 2001, in Västerås.

The SALSART tool suite
As a part of the project, we have developed the SALSART tool-suite for distributed schedule design and analysis to support our research. SALSART is a web-based cooperative environment for the design of real-time schedules. It comprises a set of stand alone tools interacting via an internet based central supervisor. It envisions a set of experts working as geographically separated team on application specification, scheduling, editing, simulation and analysis of real-time schedules.



  1. Damir Isovic, Handling Sporadic Tasks in Real-time Systems - Combined Offline and Online Approach. Licentiate thesis , Mälardalen University Press, June 2001.
  2. Damir Isovic, Gerhard Fohler: Handling Sporadic Tasks in Off-line Scheduled Distributed Real - Time Systems, 11th EUROMICRO Conference on Real-Time Systems , York, England, July 1999.
  3. Damir Isovic, Gerhard Fohler. Efficient Scheduling of Sporadic, Aperiodic, and Periodic Tasks with Complex Constraints, Proc. of the 21st IEEE Real -Time Systems Symposium, Walt Disney World, Orlando, Florida, USA, November 2000.
  4. Damir Isovic, Gerhard Fohler, Online Handling of Firm Aperiodic Tasks in Time Triggered Systems, Work-in-Progress Session, 12th EUROMICRO Conference on Real-Time Systems, Stockholm, Sweden, June 2000.
  5. Damir Isovic, Gerhard Fohler: Simulation Analysis of Sporadic and Aperiodic Task Handling, Technical Report , May 2001.
  6. Damir Isovic, Markus Lindgren, Ivica Crnkovic: System Development with Real -Time Components, Proc. of ECOOP2000 Workshop 22 - Pervasive Component-based systems, Sophia Antipolis and Cannes, France, June 2000
  7. Damir Isovic, Markus Lindgren: Real -Time Components, Technical Report , Mälardalen Real-Time Research Centre, Mälardalen University, March 2000.
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