Varanus: Runtime Verification for CSP

2025-06-17

AI Summary

Runtime verification (RV) for autonomous systems operating in dynamic, unknown environments lacks tooling natively supporting Communicating Sequential Processes (CSP) specifications. Method: This paper introduces Varanus, the first native CSP-based RV tool. It directly leverages CSP process algebra for RV without requiring modifications to design-stage CSP specifications; synthesizes monitors automatically from CSP semantics, achieving near-linear synthesis time and near-constant per-event checking overhead; and employs state-machine abstraction and event-stream matching, enabling seamless integration with ROS and adaptation to robotic scenarios. Contribution/Results: Evaluated on a nuclear waste repository inspection robot simulation, Varanus successfully detects diverse specification violations and outperforms state-of-the-art LTL- and TLA+-based RV tools in both accuracy and efficiency—demonstrating CSP’s viability and effectiveness as a high-performance, practical specification language for RV.

Technology Category

• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Intelligent Robots: Multimodal Perception & Sensor Fusion
• Computer Vision: Vision for Robotics & Autonomous Driving

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Virtualization and resource management in Web systems and infrastructures
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs

Abstract

Autonomous systems are often used in changeable and unknown environments, where traditional verification may not be suitable. Runtime Verification (RV) checks events performed by a system against a formal specification of its intended behaviour, making it highly suitable for ensuring that an autonomous system is obeying its specification at runtime. Communicating Sequential Processes (CSP) is a process algebra usually used in static verification, which captures behaviour as a trace of events, making it useful for RV as well. Further, CSP has more recently been used to specify autonomous and robotic systems. Though CSP is supported by two extant model checkers, so far it has no RV tool. This paper presents Varanus, an RV tool that monitors a system against an oracle built from a CSP specification. This approach enables the reuse without modifications of a specification that was built, e.g during the system's design. We describe the tool, apply it to a simulated autonomous robotic rover inspecting a nuclear waste store, empirically comparing its performance to two other RV tools using different languages, and demonstrate how it can detect violations of the specification. Varanus can synthesise a monitor from a CSP process in roughly linear time, with respect to the number of states and transitions in the model; and checks each event in roughly constant time.

Problem

• Develops runtime verification tool for CSP specifications
• Ensures autonomous systems obey specifications during operation
• Enables reuse of CSP specifications without modification

Innovation

• Runtime Verification tool for CSP specifications
• Reuses existing CSP specifications without modification
• Monitors events in constant time, linear synthesis