Schematic representation of RedeR data packing and storing. (a) Data structure. The software emulates a mixed graph with two layers and multiple levels in order to organize and manage the hierarchical associations. (b) Data abstraction. For the end-user, the data abstraction corresponds to the network layout that represents the data structure. A flat network is shown to contrast an ordinary representation (left) with RedeR hierarchical topology (right). (c) Data encapsulation: end-users and R developers have access to the outer level of the application through the methods handled by the interface.