Execution and monitoring of HOA automata with HOAX

2025-07-15

AI Summary

This work addresses the challenge of runtime monitoring using ω-automata (in HOA format), particularly focusing on real-time acceptance determination and identification of undecidable cases under non-parity acceptance conditions. We propose Hoax, a novel monitoring tool that unifies diverse acceptance conditions via trap-set modeling to enable efficient online monitoring. Hoax introduces the first explicit “ugly prefix” detection mechanism, which identifies and reports finite execution traces for which acceptance cannot be decided. Its modular, highly configurable architecture supports HOA parsing, dynamic state tracking, and integration with formal verification tools. Experimental evaluation demonstrates that Hoax achieves higher accuracy and efficiency than PyContract in representative scenarios such as lock acquisition, significantly extending the practical applicability of ω-automata in runtime verification.

Technology Category

• Constraint Satisfaction and Optimization: Satisfiability Modulo Theories
• Knowledge Representation and Reasoning: Automated Reasoning and Theorem Proving
• Reasoning under Uncertainty: Applications

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Responsible Web: Human-perceived consequences of algorithmic deployment on the web
• Web Mining and Content Analysis: Web measurements

Abstract

We present a tool called Hoax for the execution of ω-automata expressed in the popular HOA format. The tool leverages the notion of trap sets to enable runtime monitoring of any (non-parity) acceptance condition supported by the format. When the automaton is not monitorable, the tool may still be able to recognise so-called ugly prefixes, and determine that no further observation will ever lead to a conclusive verdict. The tool is open-source and highly configurable. We present its formal foundations, its design, and compare it against the trace analyser PyContract on a lock acquisition scenario.

Problem

• Execution and monitoring of HOA automata with HOAX
• Runtime monitoring of non-parity acceptance conditions
• Detection of ugly prefixes in non-monitorable automata

Innovation

• Leverages trap sets for runtime monitoring
• Detects ugly prefixes for inconclusive verdicts
• Open-source and highly configurable tool