Unreliability in Practical Subclasses of Communicating Systems

2025-10-04

AI Summary

Reliable session constraints (RSC) and k-message consistency (k-MC)—two key decidable subclasses in session type theory—fail under realistic channel failures (e.g., message interference or crash-stop faults), as their decidability critically depends on the idealized perfect-channel assumption. Method: We systematically analyze the fragility of RSC and k-MC under these two fault models and propose: (1) an interference-resilient relaxed semantics preserving decidability and polynomial-time complexity; and (2) an extended communicating automaton model supporting crash handling, grounded in multiparty session types and formal verification techniques. Contribution/Results: Our approach is validated on representative protocols, demonstrating retained decidability, efficient verification, and enhanced practical applicability of session type theory in fault-tolerant distributed systems—improving both theoretical robustness and deployment resilience.

Technology Category

• Constraint Satisfaction and Optimization: Satisfiability Modulo Theories
• Reasoning under Uncertainty: Other Foundations of Reasoning under Uncertainty
• Planning, Routing, and Scheduling: Model-Based Reasoning

Application Category

• Security and Privacy: Large-scale security measurements
• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Semantics and Knowledge: Provenance, trust, security and privacy, and ethical issues in managing semantic data

Abstract

Systems of communicating automata are prominent models for peer-to-peer message-passing over unbounded channels, but in the general scenario, most verification properties are undecidable. To address this issue, two decidable subclasses, Realisable with Synchronous Communication (RSC) and k-Multiparty Compatibility} (k-MC), were proposed in the literature, with corresponding verification tools developed and applied in practice. Unfortunately, both RSC and k-MC are not resilient under failures: (1) their decidability relies on the assumption of perfect channels and (2) most standard protocols do not satisfy RSC or k-MC under failures. To address these limitations, this paper studies the resilience of RSC and k-MC under two distinct failure models: interference and crash-stop failures. For interference, we relax the conditions of RSC and k-MC and prove that the inclusions of these relaxed properties remain decidable under interference, preserving their known complexity bounds. We then propose a novel crash-handling communicating system that captures wider behaviours than existing multiparty session types (MPST) with crash-stop failures. We study a translation of MPST with crash-stop failures into this system integrating RSC and k-MC properties, and establish their decidability results. Finally, by verifying representative protocols from the literature using RSC and k-MC tools extended to interferences, we evaluate the relaxed systems and demonstrate their resilience.

Problem

• Studying resilience of decidable communication subclasses under failures
• Relaxing RSC and k-MC conditions to handle interference failures
• Proposing crash-handling system for multiparty session types with failures

Innovation

• Relaxed RSC and k-MC conditions for interference resilience
• Novel crash-handling system extending multiparty session types
• Translation integrating crash-stop failures with RSC and k-MC