The classical Hennessy-Milner theorem says that two states of an image-finite transition system are bisimilar if and only if they satisfy the same formulas in a certain modal logic. In this paper we study this type of result in a general context, moving from transition systems to coalgebras and from bisimilarity to coinductive predicates. We formulate when a logic fully characterises a coinductive predicate on coalgebras, by providing suitable notions of adequacy and expressivity, and give sufficient conditions on the semantics. The approach is illustrated with logics characterising similarity, divergence and a behavioural metric on automata.
@InProceedings{kupke_et_al:LIPIcs.CSL.2020.26, author = {Kupke, Clemens and Rot, Jurriaan}, title = {{Expressive Logics for Coinductive Predicates}}, booktitle = {28th EACSL Annual Conference on Computer Science Logic (CSL 2020)}, pages = {26:1--26:18}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-132-0}, ISSN = {1868-8969}, year = {2020}, volume = {152}, editor = {Fern\'{a}ndez, Maribel and Muscholl, Anca}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2020.26}, URN = {urn:nbn:de:0030-drops-116698}, doi = {10.4230/LIPIcs.CSL.2020.26}, annote = {Keywords: Coalgebra, Fibration, Modal Logic} }
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