Modules connected to each other form a network. So, a modular robot is a module network. In the case of reconfigurable robots, the topology of this network evolves. We propose to ground the study of self-reconfigurable robots in a framework inspired by graph theory and cellular automata. We separate topological aspects from metrical ones, by defining the notion of graph topodynamic, and we provide a distributed algorithm which transforms a quadruped robot into a chain.