segments) are designated with numbers (1 through 5) while Complex Discourse Units are represented by π 1 and π 2 , dashed lines indicating member-hood in a CDU.
we consider an SDRT discourse structure as a graph, , with a set V of discourse units; two types of edges, E 1 (relations) and E 2 (CDU membership), with E 1 , E 2 ⊆ V 2 ; and a labelling function : E 1 → T , where T is a set of discourse relation types.