Figure 8: Query example. The subfigures from left to right represents the consecutive steps of a query: (i) the operator sends the Q query to node O. This node forwards it to its CDS parent. The CDS parent broadcasts the query. (ii) The CDS nodes broadcasts the query, so every node in the network is aware of Q. (iii) Every non-CDS node (except O) sends it response to its parent. (iv) The sum of the responses is propagated back to the parent of O (including the list of responding nodes, not on the figure), who forwards it to the operator through O.