Verification of Unbounded Client-Server Systems with Distinguishable Clients

TL;DR

This paper introduces a new approach for verifying unbounded client-server systems with distinguishable clients using a specialized logic and SMT-based bounded model checking, supported by an open source tool.

Contribution

It develops the logic $ ext{FOTL}_1$ for expressing properties of UCS and provides SMT encodings and a tool for BMC of these systems, addressing the challenge of client distinguishability.

Findings

Successfully encodes $ u$-nets and $ ext{FOTL}_1$ in SMT

Provides an open source BMC tool for UCS

Enables verification of dynamic, unbounded client-server systems

Abstract

Client-server systems are a computing paradigm in concurrent and distributed systems. We deal with unbounded client-server systems (UCS) where all clients are of the same type, interact with a single server and they may enter and exit the system dynamically. At any point in time, the number of clients is bounded, but their exact number is unknown and dynamic. To model these systems, simple Petri nets are not directly usable, so we use unbounded $\nu$-nets. Owing to the distinguishability of clients in UCS, it is not straightforward to express their properties in LTL or CTL. To address this, we propose the logic $\mathsf{FOTL_1}$, a monodic fragment of Monadic First Order Temporal Logic (MFOTL). In this work, we provide the SMT encodings of $\nu$-nets and $\mathsf{FOTL_1}$ to do Bounded Model Checking (BMC). We also build an accompanying open source tool to perform BMC of UCS.