Expressive Logics for Coinductive Predicates

The classical Hennessy-Milner theorem says that two states of an image-finite transition system are bisimilar if and only they satisfy the same formulas in a certain modal logic. In this paper we study type result general context, moving from systems to coalgebras bisimilarity coinductive predicates. We formulate when logic fully characterises predicate on coalgebras, by providing suitable notions adequacy expressivity, give sufficient conditions semantics. approach is illustrated with logics characterising similarity, divergence behavioural metric automata.