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Weakly hard real-time systems

Bernat, G., Burns, A. and Liamosi, A. (2001) Weakly hard real-time systems. IEEE Transactions on Computers, 50 (4). pp. 308-321. ISSN 0018-9340

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In a hard real-time system, it is assumed that no deadline is missed, whereas, in a soft or firm real-time system, deadlines can be missed, although this usually happens in a nonpredictable way. However, most hard real-time systems could miss some deadlines provided that it happens in a known and predictable way. Also, adding predictability on the pattern of missed deadlines for soft and firm real-time systems is desirable, for instance, to guarantee levels of quality of service. We introduce the concept of weakly hard real-time systems to model real-time systems that can tolerate a clearly specified degree of missed deadlines. For this purpose, we define four temporal constraints based on determining a maximum number of deadlines that can be missed during a window of time (a given number of invocations). This paper provides the theoretical analysis of the properties and relationships of these constraints. It also shows the exact conditions under which a constraint is harder to satisfy than another constraint. Finally, results on fixed priority scheduling and response-time schedulability tests for a wide range of process models are presented

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Computer Science (York)
Depositing User: York RAE Import
Date Deposited: 06 Aug 2009 13:32
Last Modified: 06 Aug 2009 13:32
Published Version: http://dx.doi.org/10.1109/12.919277
Status: Published
Publisher: IEEE Institute of Electrical and Electronics
Identification Number: 10.1109/12.919277
URI: http://eprints.whiterose.ac.uk/id/eprint/6199

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