Determinism in Avionics: Lack of Definition, Survey of its Use, and Taxonomy to Clarify its Meaning

The word determinism is often used but rarely defined among software practitioners in safety-critical systems. To address this, recent work [1] presented an initial taxonomy for different meanings of the word determinism—this taxonomy asked questions and provided possible answers so each assignment of answers to all questions yields a definition of determinism. It also presented how different disciplines have used the word determinism. Unfortunately, there were three gaps in [1].$1^{\text {st }}$gap: there are aspects of determinism that the taxonomy did not discuss.$2^{\text {nd }}$gap: the notion of determinism was only used for disciplines that rely on a model of computation (MoC) and it only considered some MoC.$3^{\text {rd }}$gap: there had been no actual use of the new taxonomy. Therefore, in this paper, we address these gaps by: (i) extending the taxonomy, (ii) extending the discussion on previous work to other MoC and to other disciplines, and (iii) applying the taxonomy on research papers in avionics. Addressing the$1^{\text {st }}$gap helps to clarify the notion of determinism and hence mitigate the aforementioned confusion. Addressing the$2^{\text {nd }}$gap puts the notion of determinism in perspective. Addressing the$3^{\text {rd }}$gap shows how the taxonomy distinguishes between the different types of determinism.