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FRETting About Requirements: Formalised Requirements for an Aircraft Engine Controller

Part of the Lecture Notes in Computer Science book series (LNCS,volume 13216)


[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.


  • Formal requirements
  • FRET
  • Traceability

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.

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  1. 1.

    This Paper Extended Version:

  2. 2.

    The VALU3S project:

  3. 3.


  4. 4.

    This Paper Extended Version:

  5. 5.

    “Formalising Verifiable Requirements” Presentation:


  1. Back, R.J., Wright, J.: Refinement Calculus: A Systematic Introduction. Springer, Cham (1998)

    CrossRef  Google Scholar 

  2. Barbosa, R., et al.: The VALU3S ECSEL project: verification and validation of automated systems safety and security. In: Euromicro Conference on Digital System Design, pp. 352–359. IEEE (2020)

    Google Scholar 

  3. Bourbouh, H., et al.: Integrating formal verification and assurance: an inspection rover case study. In: Dutle, A., Moscato, M.M., Titolo, L., Muñoz, C.A., Perez, I. (eds.) NFM 2021. LNCS, vol. 12673, pp. 53–71. Springer, Cham (2021).

  4. Bourbouh, H., Garoche, P.L., Loquen, T., Noulard, É., Pagetti, C.: CoCoSim, a code generation framework for control/command applications An overview of CoCoSim for multi-periodic discrete Simulink models. In: European Congress on Embedded Real Time Software and Systems (2020)

    Google Scholar 

  5. Darimont, R., Van Lamsweerde, A.: Formal refinement patterns for goal-driven requirements elaboration. ACM SIGSOFT Softw. Eng. Notes 21(6), 179–190 (1996)

    CrossRef  Google Scholar 

  6. Dutle, A., et al.: From requirements to autonomous flight: an overview of the monitoring ICAROUS project. In: Workshop on Formal Methods for Autonomous Systems, pp. 23–30. EPTCS (2020)

    Google Scholar 

  7. Giannakopoulou, D., Mavridou, A., Rhein, J., Pressburger, T., Schumann, J., Shi, N.: Formal requirements elicitation with FRET. In: International Conference on Requirements Engineering: Foundation for Software Quality (2020)

    Google Scholar 

  8. Giannakopoulou, D., Pressburger, T., Mavridou, A., Schumann, J.: Automated formalization of structured natural language requirements. Information and Software Technology 137, 106590 (2021)

    Google Scholar 

  9. Luckcuck, M., Farrell, M., Sheridan, O., Monahan, R.: A methodology for developing a verifiable aircraft engine controller from formal requirements. In: IEEE Aerospace Conference (2022)

    Google Scholar 

  10. Mavridou, A., Bourbouh, H., Garoche, P.L., Giannakopoulou, D., Pessburger, T., Schumann, J.: Bridging the gap between requirements and simulink model analysis. In: International Conference on Requirements Engineering: Foundation for Software Quality (2020)

    Google Scholar 

  11. Mavridou, A., et al.: The ten lockheed martin cyber-physical challenges: formalized, analyzed, and explained. In: International Requirements Engineering Conference, pp. 300–310. IEEE (2020)

    Google Scholar 

  12. Perez, I., Dedden, F. and Goodloe, A.: Copilot 3. Technical report, NASA/TM-2020-220587, National Aeronautics and Space Administration (2020)

    Google Scholar 

  13. Postlethwaite, I., Samar, R., Choi, B.W., Gu, D.W.: A digital multimode H\(\infty \) controller for the Spey Turbofan engine. In: European Control Conference (1995)

    Google Scholar 

  14. Samar, R., Postlethwaite, I.: Design and implementation of a digital multimode H\(\infty \) controller for the Spey Turbofan engine. J. Dyn. Syst. Measur. Control 132(1), 011010 (2010)

    Google Scholar 

  15. Zave, P., Jackson, M.: Four dark corners of requirements engineering. ACM Trans. Softw. Eng. Methodol. (TOSEM) 6(1), 1–30 (1997)

    CrossRef  Google Scholar 

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Correspondence to Marie Farrell .

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Farrell, M., Luckcuck, M., Sheridan, O., Monahan, R. (2022). FRETting About Requirements: Formalised Requirements for an Aircraft Engine Controller. In: Gervasi, V., Vogelsang, A. (eds) Requirements Engineering: Foundation for Software Quality. REFSQ 2022. Lecture Notes in Computer Science, vol 13216. Springer, Cham.

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