Nancy.Expressions: Towards a Computer Algebra System for Deterministic Network Calculus

Deterministic Network Calculus (DNC) is a mathematical framework for the worst-case analysis of networked systems. In lessthan- trivial cases, pen-and-paper computation of DNC expressions is not viable, and the support of a software library for the automated computation is instead required. Existing software libraries for DNC focus on computing single operations, lacking the ability to manipulate symbolic expressions. On the other hand, a Computer Algebra System (CAS) for DNC needs means to efficiently construct, visualize, manipulate and simplify complex expressions, to automatically optimize computation runtimes. To address this gap, we developed Nancy.Expressions, an open-source library which can work on arbitrarily complex DNC symbolic expressions. It is designed for ease of adoption, in particular for projects based on the Nancy library. The library is able to analyze an expression and apply equivalences and properties before making any computation, possibly reducing its complexity. It includes a specialized grammar, that enables the user to define new properties to simplify expressions. In this paper we present this library in its goals, architecture and semantics, highlighting with examples its ease of adoption and capabilities for performance optimizations.