,
Stefan Kiefer
,
David Parker
,
Franck van Breugel
Creative Commons Attribution 4.0 International license
The probabilistic bisimilarity distance provides a quantitative measure of behavioural difference for labelled Markov chains, but it may be discontinuous under perturbations of the transition probabilities. This lack of continuity undermines its applicability to empirically derived models, where transition probabilities are often approximations. Recently, we introduced robust probabilistic bisimilarity as a sufficient condition for continuity at distance zero. In this paper, we show that it is also a necessary condition, that is, two states are robustly probabilistic bisimilar if and only if their probabilistic bisimilarity distance is small for any small enough perturbation of the transition probabilities. We further extend robustness to non-bisimilar state pairs to establish a complete characterization for continuity of the probabilistic bisimilarity distance. Based on this characterization, we develop a polynomial time algorithm to decide continuity. Finally, we complement our theoretical contributions with an experimental evaluation demonstrating the proposed approach in practice. Our results show that the extra step of deciding continuity requires minimal additional cost when compared to computing the probabilistic bisimilarity distance.
@InProceedings{fatmi_et_al:LIPIcs.CONCUR.2026.34,
author = {Fatmi, Syyeda Zainab and Kiefer, Stefan and Parker, David and van Breugel, Franck},
title = {{On the Continuity of the Probabilistic Bisimilarity Distance}},
booktitle = {37th International Conference on Concurrency Theory (CONCUR 2026)},
pages = {34:1--34:18},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-447-5},
ISSN = {1868-8969},
year = {2026},
volume = {391},
editor = {Sokolova, Ana and Totzke, Patrick},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2026.34},
URN = {urn:nbn:de:0030-drops-273648},
doi = {10.4230/LIPIcs.CONCUR.2026.34},
annote = {Keywords: probabilistic model checking, labelled Markov chain, probabilistic bisimilarity distance}
}
archived version
archived version