Coequational Logic for Finitary Functors

Coequations, which are subsets of a cofree coalgebra, can be viewed as properties of systems. In case of a polynomial functor, a logic of coequations was formulated by J. Adámek. However, the logic is more complicated for other functors than polynomial ones, and simple deduction rules can no longer be formulated. A simpler coequational logic for finitely branching labelled transition systems was later presented by the author. The current paper carries that research further: it yields a simple coequational logic for finitary functors that preserve preimages. Furthermore we prove a statement for semantical consequences of sets of coequations in the case of accessible functors.