FRETting About Requirements: Formalised Requirements for an Aircraft Engine Controller

Abstract

[Context & motivation] Eliciting requirements that are detailed and logical enough to be amenable to formal verification is a difficult task. Multiple tools exist for requirements elicitation and some of these also support formalisation of requirements in a way that is useful for formal methods. [Question/problem] This paper reports on our experience of using the Formal Requirements Elicitation Tool (FRET) alongside our industrial partner. The use case that we investigate is an aircraft engine controller. In this context, we evaluate the use of FRET to bridge the communication gap between formal methods experts and aerospace industry specialists. [Principal ideas/results] We describe our journey from ambiguous, natural-language requirements to concise, formalised FRET requirements. We include our analysis of the formalised requirements from the perspective of patterns, translation into other formal methods and the relationship between parent-child requirements in this set. We also provide insight into lessons learned throughout this process and identify future improvements to FRET. [Contribution] Previous experience reports have been published by the FRET team, but this is the first such report of an industrial use case that was written by researchers that have not been involved FRET’s development.

Keywords

The authors thank Georgios Giantamidis, Stylianos Basagiannis, and Vassilios A. Tsachouridis (UTRC, Ireland) for their help in requirements elicitation; and Anastasia Mavridou (NASA Ames Research Center, USA) for her help with FRET. This research was funded by the European Union’s Horizon 2020 research and innovation programme under the VALU3S project (grant No. 876852), and by Enterprise Ireland (grant No. IR20200054). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.