Figure 2

The embedding of a feed-forward loop (FFL) instance into a network. The FFL pattern is given here by the coherence between the vertices X, Y, Z. Therewith its only instance consists of these vertices and the intrinsic edges X → Y, Y → Z, X → Z. How the FFL instance relates to the rest of the network is determined by those kinds of extrinsic edges that are attached to the vertices X, Y, Z (blue dotted edges). Other extrinsic edges link further vertices (blue vertices) in the environment of the FFL instances. The connection between a pair of vertices can be affected only then by the FFL instance if the paths linking them contain at least one of the intrinsic edges. For example, the connection between the pair (E₂, E₆) depends of the relation between the vertices X, Y, Z. In contrast, there still is an alternative path between the vertices E₂ and Y that remains untouched. Note that the 'feed-forwarding' action of the FFL instance does not apply to those paths which cross only one intrinsic edge of this instance – e.g., path {E₁, E₂, X, Y, E₈, E₉} and path {E₃, E₄, Y, Z, E₆, E₇}.