Predictive Varanus: Combining CSP Conformance Monitoring with Predictive LTL Runtime Verification

Predictive Varanus: Combining CSP Conformance Monitoring with Predictive LTL Runtime Verification

Angelo Ferrando, Matt Luckcuck, Pedro Ribeiro · N/A · 2026

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Summary

Runtime Verification is well suited to autonomous and robotic systems because it checks the behaviour that is actually observed during execution. Its main limitation, however, is that it is usually reactive: the monitor detects a violation only after the system has already performed a bad event.

Abstract Summary

Runtime Verification is well suited to autonomous and robotic systems because it checks the behaviour that is actually observed during execution. Its main limitation, however, is that it is usually reactive: the monitor detects a violation only after the system has already performed a bad event. This can be too late in domains where failures are costly or unsafe. In this paper we present PREDICTIVE VARANUS, a two-stage verification pipeline that combines VARANUS, a runtime verifier that uses models written in the process algebra Communicating Sequential Processes (CSP), with predictive runtime verification for LTL. A CSP model is first used as a conformance gate over the observed event trace; the same model is then translated into a Buchi automaton that constrains the futures explored by a predictive LTL monitor. In this way, out-of-model behaviour is rejected immediately, while model-consistent prefixes can be classified as already guaranteeing satisfaction, already forcing violation, or still being inconclusive for the monitored temporal property. We formalise the combined monitor, explain its implementation, and illustrate the approach on a robotic rover for nuclear-store inspection. The case study shows how the combination of CSP validation and predictive LTL can provide earlier verdicts than standard runtime monitoring while reusing an existing design-time CSP model.

Key Points

  • Runtime Verification is well suited to autonomous and robotic systems because it checks the behaviour that is actually observed during execution.
  • Its main limitation, however, is that it is usually reactive: the monitor detects a violation only after the system has already performed a bad event.
  • This can be too late in domains where failures are costly or unsafe
  • In this paper we present PREDICTIVE VARANUS, a two-stage verification pipeline that combines VARANUS, a runtime verifier that uses models written in the process algebra Communicating Sequential Processes (CSP), with predictive runtime verification for LTL.
  • A CSP model is first used as a conformance gate over the observed event trace; the same model is then translated into a Buchi automaton that constrains the futures explored by a predictive LTL monitor.

Predictive Varanus

Figure 1 shows the components in the Predictive Varanus pipeline. The SUA emits a trace of events. Each event is checked by Varanus for validity with the CSP model, if it is a valid event then it is passed to the Predictive LTL Monitor. The predictive monitor projects the event into the propositional alphabet, and uses the Büchi automaton (translated from the CSP model) to perform PRV .

In this way, the predictive component never reasons about futures for events that Varanus has already rejected as invalid.

Predictive Varanus — Predictive Varanus: Combining CSP Conformance Monitoring with Predictive LTL Runtime Verification
Fig. 1: The Predictive Varanus verification pipeline. A CSP model is reused both as a runtime conformance gate through Varanus and as the source of the Büchi automaton used by the predictive LTL monitor.

Case Study

To evaluate Predictive Varanus , we reuse the example of an autonomous rover patrolling a simulated nuclear waste store, and reuse the CSP model of the rover, that we used in our earlier Varanus work [ 7 ] . The rover’s mission is to inspect the radiation levels at various waypoints.

The radiation readings are categorised into Green , Orange , or Red ; if the radiation is Green then the mission can continue, but Orange , or Red mean that the rover should return to the entry point and abort the mission.

Evaluation

This section presents two evaluations of Predictive Varanus 1 1 1 Predictive Varanus available at: https://github.com/AngeloFerrando/PredictiveVaranus . . First, we study the rover mission from Sect. IV to validate the verdicts and quantify the practical benefit of the approach.

Second, we conduct a quantitative stress test on synthetic CSP models to assess computational overhead and scalability under controlled variations of model size, branching structure, and termination depth.

Sources and Demonstrations

Figures are reproduced from Ferrando et al. See the full paper for experimental details and the project page, when the paper links one, for demonstrations and videos.

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