Interpretation of graph and module labels for systematic PCP experiments. (a) Two neighbors in the network are proteins occurring in a same complex. (b) Several potential sets of complexes can be the origin of the same observed network. Restricting interpretation to the simplest model (top right), the series module reads as a logical AND between its members. (c) A module labeled parallel corresponds to proteins or modules working as strict alternatives with respect to their common neighbors. (d) The prime case is a structure where none of the two previous cases occurs. Symbols are as in Figure 2.