The subobject classifier of the category of functional bisimulations (Q1301354)

The author investigates a category of nondeterministic dynamical systems and functional bisimulations between them. He shows that this category may be regarded as the category of coalgebras for the `nonempty finite subsets' functor on the category of sets, and that it possesses a subobject classifier. The latter result has since been generalized to a large class of similar categories of coalgebras in a paper by \textit{H. Watanabe, P. T. Johnstone, J.~Power, T.~Tsujishita} and \textit{J.~Worrell} [Theor. Comput. Sci. (to appear)].