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Comparing Degrees of Non-Determinism in Expression Evaluation

Lookup NU author(s): Professor Ian Hayes, Professor Cliff JonesORCiD


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Expression evaluation in programming languages is normally assumed to be deterministic; however, if an expression involves variables that are being modified by the environment of the process during its evaluation, the result of the evaluation can be nondeterministic. Two common scenarios in which this occurs are concurrent programs within which processes share variables and real- time programs that interact to monitor and/or control their environment. In these contexts, although any particular evaluation of an expression gives a single result, there is a range of possible values that could be returned depending on the relative timing between modification to a variable by the environment and its access within the expression evaluation. To compare the semantics of nondeterministic expression evaluation, one can use the set of possible values the expression evaluation could return. This paper formalises three approaches to nondeterministic expression evaluation, highlights their commonalities and differences, shows the relationships between the approaches and explores conditions under which they coincide. Modal operators representing that a predicate holds for all possible evaluations and for some possible evaluation are associated with each of the evaluation approaches, and the properties and relationships between these operators are investigated. Furthermore, a link is made to a new notation used in reasoning about interference.

Publication metadata

Author(s): Hayes IJ, Burns A, Dongol B, Jones CB

Publication type: Article

Publication status: Published

Journal: The Computer Journal

Year: 2013

Volume: 56

Issue: 6

Pages: 741-755

Print publication date: 05/02/2013

ISSN (print): 0010-4620

ISSN (electronic): 1460-2067

Publisher: Oxford University Press


DOI: 10.1093/comjnl/bxt005


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Funder referenceFunder name
DP0987452Australian Research Council (ARC)