Let M be a system (possibly proper class-sized directed graph where the class of children of a given node is a set). A binary relation R on M is a BISIMULATION if [tex]R\subset R'[/tex], where for [tex]a, b\in M[/tex] [tex]aR'b \Leftrightarrow ((\forall x \in a_M\exists y\in b_M xRy) \wedge (\forall x \in b_M\exists y\in a_M xRy))[/tex] where [tex]a_M[/tex] is the set of children of a in M. So let ~ be the relation on the class of all sets V such that a~b iff there exists an accessible pointed graph that is the picture of both a and b. An accessible pointed graph is a directed graph with a distinguished node from where every other node is connected by a path. Show that ~ is a bisimulation. I'm not sure what bisimulation says. Can someone explain it in more familiar terms?