A relation R between single-coloured
flow graphs G1 and G2 is a relation between
nodes and a relation between edges, which respect
labels, incoming edges and outgoing edges.
An almost simulation is a relation R
such that:
If
E1
in G1
and E1 R E2
then
E2
in G2
and N1 R N2.
R is an almost bisimulation iff R and
R-1 are almost simulations.