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Towards an Argument Pattern for the Use of Safety Performance Indicators

Daniel Ratiu, Tihomir Rohlinger, Torben Stolte, Stefan Wagner

TL;DR

This paper presents the initial work towards an argument pattern for the use of SPIs to ensure validity of safety cases throughout the entire lifecycle of the system, and proposes an approach to continuously monitor their expected performance by using meta-SPIs.

Abstract

UL 4600, the safety standard for autonomous products, mandates the use of Safety Performance Indicators (SPIs) to continuously ensure the validity of safety cases by monitoring and taking action when violations are identified. Despite numerous examples of concrete SPIs available in the standard and companion literature, their contribution rationale for achieving safety is often left implicit. In this paper, we present our initial work towards an argument pattern for the use of SPIs to ensure validity of safety cases throughout the entire lifecycle of the system. Our aim is to make the implicit argument behind using SPIs explicit, and based on this, to analyze the situations that can undermine confidence in the chosen set of SPIs. To maintain the confidence in SPIs' effectiveness, we propose an approach to continuously monitor their expected performance by using meta-SPIs.

Towards an Argument Pattern for the Use of Safety Performance Indicators

TL;DR

This paper presents the initial work towards an argument pattern for the use of SPIs to ensure validity of safety cases throughout the entire lifecycle of the system, and proposes an approach to continuously monitor their expected performance by using meta-SPIs.

Abstract

UL 4600, the safety standard for autonomous products, mandates the use of Safety Performance Indicators (SPIs) to continuously ensure the validity of safety cases by monitoring and taking action when violations are identified. Despite numerous examples of concrete SPIs available in the standard and companion literature, their contribution rationale for achieving safety is often left implicit. In this paper, we present our initial work towards an argument pattern for the use of SPIs to ensure validity of safety cases throughout the entire lifecycle of the system. Our aim is to make the implicit argument behind using SPIs explicit, and based on this, to analyze the situations that can undermine confidence in the chosen set of SPIs. To maintain the confidence in SPIs' effectiveness, we propose an approach to continuously monitor their expected performance by using meta-SPIs.
Paper Structure (27 sections, 5 figures)

This paper contains 27 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Approach.
  3. Structure.
  4. Background
  5. Structured Safety Arguments,
  6. UL4600 2023_ul4600
  7. A High-level Argument Structure for Using SPIs
  8. Top Level.
  9. Systematic Definition of SPIs
  10. Goal 1.1.1 -- Sufficient Coverage of SPIs.
  11. Goal 1.1.2 - Rigorous Management of SPIs.
  12. Collection and Analysis of SPIs
  13. Goal 1.2.1 -- Dependable Collection of SPI Violations.
  14. Goal 1.2.2 -- Analysis of SPI Violations
  15. Response to SPI Violations
  16. ...and 12 more sections

Figures (5)

  • Figure 1: Our approach at a glance.
  • Figure 2: Top-level argument about the use of the SPIs framework for maintaining the validity of a safety case {SC} through the life-cycle of a product.
  • Figure 3: Argument leg about the definition of SPIs.
  • Figure 4: Argument leg about the collection and analysis of SPIs.
  • Figure 5: Argument leg about the response to SPIs violations.