University of Hertfordshire

By the same authors

ODRE Workshop: Using SIL Arithmetic to Design Safe and Secure Systems

Research output: Chapter in Book/Report/Conference proceedingConference contribution


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Original languageEnglish
Title of host publicationProceedings - 2020 IEEE 23rd International Symposium on Real-Time Distributed Computing, ISORC 2020
Number of pages6
ISBN (Electronic)9781728169583
ISBN (Print)9781728169590
Publication statusPublished - 21 May 2020
Event23rd International Symposium on Real-Time Distributed Computing - Nashville, United States
Duration: 19 May 202021 May 2020

Publication series

NameProceedings - 2020 IEEE 23rd International Symposium on Real-Time Distributed Computing, ISORC 2020


Conference23rd International Symposium on Real-Time Distributed Computing
Abbreviated titleISORC 2020
Country/TerritoryUnited States
Internet address


In a safety-critical system each service has a specific level of safety criticality. Safety standards use classifications like Safety Integrity Levels (SIL), to describe the design requirements for the individual services of a system. Techniques like redundancy can be used to achieve a higher overall dependability than the used individual components provide. Using the notion of SIL, this can be called SIL arithmetic. In this paper we describe the concept of SIL arithmetic and point out how different safety standards provide hints for their support of using SIL arithmetic. We highlight the principal benefits of SIL arithmetic and provide simple examples. But the use of SIL arithmetic in a concrete system design can also have its pitfalls, which we also discuss in this paper. We specifically discuss these issues in the context of scheduling techniques for mixed-criticality systems, where resource shortages are to be handled by the scheduler.


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