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Quantitative Hennessy-Milner Theorems via Notions of Density

Authors Jonas Forster , Sergey Goncharov , Dirk Hofmann , Pedro Nora , Lutz Schröder , Paul Wild

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Jonas Forster
  • Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
Sergey Goncharov
  • Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
Dirk Hofmann
  • CIDMA, University of Aveiro, Portugal
Pedro Nora
  • Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
Lutz Schröder
  • Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
Paul Wild
  • Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany

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Jonas Forster, Sergey Goncharov, Dirk Hofmann, Pedro Nora, Lutz Schröder, and Paul Wild. Quantitative Hennessy-Milner Theorems via Notions of Density. In 31st EACSL Annual Conference on Computer Science Logic (CSL 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 252, pp. 22:1-22:20, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)


The classical Hennessy-Milner theorem is an important tool in the analysis of concurrent processes; it guarantees that any two non-bisimilar states in finitely branching labelled transition systems can be distinguished by a modal formula. Numerous variants of this theorem have since been established for a wide range of logics and system types, including quantitative versions where lower bounds on behavioural distance (e.g. in weighted, metric, or probabilistic transition systems) are witnessed by quantitative modal formulas. Both the qualitative and the quantitative versions have been accommodated within the framework of coalgebraic logic, with distances taking values in quantales, subject to certain restrictions, such as being so-called value quantales. While previous quantitative coalgebraic Hennessy-Milner theorems apply only to liftings of set functors to (pseudo)metric spaces, in the present work we provide a quantitative coalgebraic Hennessy-Milner theorem that applies more widely to functors native to metric spaces; notably, we thus cover, for the first time, the well-known Hennessy-Milner theorem for continuous probabilistic transition systems, where transitions are given by Borel measures on metric spaces, as an instance of such a general result. In the process, we also relax the restrictions imposed on the quantale, and additionally parametrize the technical account over notions of closure and, hence, density, providing associated variants of the Stone-Weierstraß theorem; this allows us to cover, for instance, behavioural ultrametrics.

Subject Classification

ACM Subject Classification
  • Theory of computation → Modal and temporal logics
  • Theory of computation → Concurrency
  • Behavioural distances
  • coalgebra
  • characteristic modal logics
  • density
  • Hennessy-Milner theorems
  • quantale-enriched categories
  • Stone-Weierstraß theorems


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