  Causal Graph Dynamics generalize Cellular Automata, extending them to bounded
degree, time varying graphs. The dynamics rewrite the graph at each time step
with respect to two physics-like symmetries: causality (bounded speed of
information) and homogeneity (the rewriting acts the same everywhere on the
graph, at every time step). Universality is the ability simulating every other
instances of another (or the same) model of computation. In this work, we study
three different notions of simulation for Causal Graph Dynamics, each of them
leading to a definition of universality.
