# Operational Semantics of Process Monitors

## TL;DR

This paper develops an SOS-style operational semantics for CSPe, a runtime monitor specification language, to improve understanding, correctness, and further study of its properties and implementation.

## Contribution

It introduces the first operational semantics for CSPe, explicitly handling failures, enabling better correctness proofs and further research.

## Key findings

- Operational semantics for CSPe successfully models explicit failures.
- Provides a foundation for correctness and optimization of CSPe implementations.
- Facilitates further study of CSPe's properties and runtime verification applications.

## Abstract

CSPe is a specification language for runtime monitors that can directly express concurrency in a bottom-up manner that composes the system from simpler, interacting components. It includes constructs to explicitly flag failures to the monitor, which unlike deadlocks and livelocks in conventional process algebras, propagate globally and aborts the whole system's execution. Although CSPe has a trace semantics along with an implementation demonstrating acceptable performance, it lacks an operational semantics. An operational semantics is not only more accessible than trace semantics but also indispensable for ensuring the correctness of the implementation. Furthermore, a process algebra like CSPe admits multiple denotational semantics appropriate for different purposes, and an operational semantics is the basis for justifying such semantics' integrity and relevance. In this paper, we develop an SOS-style operational semantics for CSPe, which properly accounts for explicit failures and will serve as a basis for further study of its properties, its optimization, and its use in runtime verification.