Figure 2

(a) G with marked v (b) G \ { v } An example to show how G \ {v} is computed. v is marked on G in (a). Note that v has two red and one green outgoing edges; it has one red and one green incoming edge. When v is removed, one of the new red strands is labeled by the set {d, c} and the new green strand is labeled by the singleton q. The resulting edges and labels are shown in (b). [Note that vertex v is a resolvable node in G.]