Towards a compositional semantics for quantitative confidence assessment in assurance arguments

2026-05-21

AI Summary

This work addresses the limitation of existing assurance argumentation methods, such as Goal Structuring Notation (GSN), which lack an operational semantics for confidence and thus struggle to quantitatively assess claim credibility under incomplete, conflicting, or subjective evidence. To overcome this, the paper proposes a compositional semantic framework grounded in Subjective Logic (SL), modeling GSN elements as SL opinions and capturing their dependencies through SL operators to construct a traceable, context-aware confidence propagation network. This approach provides, for the first time, a unified confidence semantics encompassing all GSN elements and relationships, enabling end-to-end quantitative confidence assessment fully compatible with GSN. Case studies demonstrate the feasibility and effectiveness of the proposed framework in practical applications.

Abstract

Assurance arguments provide a clear and structured way to explain why stakeholders should trust that a system satisfies certain properties, yet widely used notations, e.g.Goal Structuring Notation (GSN), typically lack an operational semantics for deriving assurance confidence. Existing approaches address structure and soundness but largely reason over truth values, not over confidence in the justification of claims. Subjective Logic (SL) offers a calculus of belief, disbelief, and uncertainty with operators for combining opinions, enabling confidence propagation under incomplete, conflicting, or subjective evidence. However, existing SL-based approaches do not provide a uniform, compositional semantics that covers all argument elements and relations to enable overall confidence assessment. We propose a confidence semantics that represents argument elements as SL opinions and maps relations between elements to SL operators modelling how confidence flows, effectively turning the argument into an analyzable confidence network. The approach provides explicit warrants, principled handling of context, preserved provenance, and compatibility with GSN, along with practical guidance using an exemplary assurance confidence assessment.

Problem

• assurance arguments
• confidence assessment
• compositional semantics
• Subjective Logic
• Goal Structuring Notation

Innovation

• compositional semantics
• Subjective Logic
• confidence propagation
• assurance arguments
• Goal Structuring Notation