The Pyramis Library: Efficient Numerical Evaluation of Hierarchical UML Statecharts Applied to Stochastic Workflows

Carnevali L, German R, Montecchi L, Scommegna L, Vicario E (2026)

Publication Type: Conference contribution

Publication year: 2026

Journal

Lecture Notes in Computer Science Springer Verlag

Publisher: Springer Science and Business Media Deutschland GmbH

Book Volume: 15657 LNCS

Pages Range: 131-146

Conference Proceedings Title: Lecture Notes in Computer Science

Event location: Catania, ITA

ISBN: 9783032163448

DOI: 10.1007/978-3-032-16345-5_10

Abstract

Pyramis is a library for quantitative evaluation of hierarchical UML statecharts with non-Markovian stochastic timing and probabilistic choices. It implements an efficient numerical approach for transient analysis until absorption and steady-state analysis, separately evaluating the Semi-Markov Process (SMP) of each model component. As Pyramis facilitates code reusability, maintainability, and extensibility, it has been easily integrated with the FaultFlow library for dependability analysis of component-based systems, supporting efficient quantitative evaluation of stochastic static fault trees without repeated events. In this paper, we use Pyramis for quantitative evaluation of workflows where activities have non-Markovian stochastic duration and where precedence constraints define a Directed Acyclic Graph (DAG). Workflows have a Service Level Objective (SLO) on their end-to-end (E2E) response time distribution at low workloads of requests. Pyramis efficiently derives the workflow E2E response time distribution, yielding a stochastic upper bound for topologies with non-well-nested precedence DAGs. In our experiments, we consider a workflow with topology derived from a real benchmark and execution times obtained from a known dataset. We report results for workflow variants obtained by increasing the number of sequential, concurrent, or alternative activities of workflow patterns. Results are promising in terms of tradeoff between accuracy and complexity.

Authors with CRIS profile

Reinhard German Computer Science 7 (Computer Networks and Communication Systems)

Involved external institutions

NTNU Trondheim - Norwegian University of Science and Technology NO Norway (NO) Università degli Studi di Firenze / University of Florence IT Italy (IT)

How to cite

APA:

Carnevali, L., German, R., Montecchi, L., Scommegna, L., & Vicario, E. (2026). The Pyramis Library: Efficient Numerical Evaluation of Hierarchical UML Statecharts Applied to Stochastic Workflows. In Laura Carnevali, Josu Doncel (Eds.), Lecture Notes in Computer Science (pp. 131-146). Catania, ITA: Springer Science and Business Media Deutschland GmbH.

MLA:

Carnevali, Laura, et al. "The Pyramis Library: Efficient Numerical Evaluation of Hierarchical UML Statecharts Applied to Stochastic Workflows." Proceedings of the 21st European Workshop on Computer Performance Engineering, EPEW 2025, Catania, ITA Ed. Laura Carnevali, Josu Doncel, Springer Science and Business Media Deutschland GmbH, 2026. 131-146.

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