A Lean Approach to Building Valid Model-Based Safety Arguments
Bibliographic record
Abstract
In recent decades, cyber-physical systems developed using Model-Driven Engineering (MDE) techniques have become ubiquitous in safety-critical domains. Safety assurance cases (ACs) are structured arguments designed to comprehensively show that such systems are safe; however, the reasoning steps, or strategies, used in AC arguments are often informal and difficult to rigorously evaluate. Consequently, AC arguments are prone to fallacies, and unsafe systems have been deployed as a result of fallacious ACs. To mitigate this problem, prior work [32] created a set of provably valid AC strategy templates to guide developers in building rigorous ACs. Yet instantiations of these templates remain error-prone and still need to be reviewed manually. In this paper, we report on using the interactive theorem prover Lean to bridge the gap between safety arguments and rigorous model-based reasoning. We generate formal, modelbased machine-checked AC arguments, taking advantage of the traceability between model and safety artifacts, and mitigating errors that could arise from manual argument assessment. The approach is implemented in an extended version of the MMINT-A model management tool [10]. Implementation includes a conversion of informal claims into formal Lean properties, decomposition into formal sub-properties and generation of correctness proofs. We demonstrate the applicability of the approach on two safety case studies from the literature.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.020 | 0.068 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.001 | 0.003 |
| Bibliometrics | 0.004 | 0.001 |
| Science and technology studies | 0.002 | 0.005 |
| Scholarly communication | 0.005 | 0.006 |
| Open science | 0.005 | 0.008 |
| Research integrity | 0.002 | 0.006 |
| Insufficient payload (model declined to judge) | 0.008 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".