Real-time systems must meet, in addition to their functional requirements, requirements regarding their timing behavior. In the case of hard real-time systems, such requirements include the absence of deadline misses. In contrast, for soft real-time systems, a “reasonable” number of deadline misses may happen without leading to a system failure. The usual definition of what a “reasonable” number of deadline misses formally means is based on probability distributions. Another option is to use weakly-hard constraints, which describe bounds on the number of allowed deadline misses in a given time window.

In this paper we show the interest of using weakly-hard constraints for other purposes than describing deadline misses, e.g. to describe execution times or jitter. We discuss in depth the semantics of weakly-hard constraints with an emphasis on how they can be inferred from other weakly-hard constraints and compared to probabilistic constraints.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Sophie Quinton
    • 1
  • Rolf Ernst
    • 1
  1. 1.Institute of Computer Network and EngineeringTU BraunschweigGermany

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