Coalgebraic modal logic and games for coalgebras with side effects

10/19/2021

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by   H. Beohar, et al.

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We study coalgebraic modal logic and games to characterise behavioural equivalence in the presence of side effects, i.e., when coalgebras live in a (co)Kleisli or an Eilenberg-Moore category. Our aim is to develop a general framework based on indexed categories/fibrations that is common, at least, to the aforementioned categories. In particular, we show how the coalgebraic notion of behavioural equivalence arises from a relation lifting (a special kind of indexed morphism) and we give a general recipe to construct such liftings in the above three cases. Lastly, we apply this framework to derive games and logical characterisations for (weighted) language equivalence and conditional bisimilarity.