Discourse structure annotations have been demonstrated to be of high utility for a number of NLP applications, including automatic text summarization (Marcu, 1998; Marcu, 1999; Cristea et al., 2005) , sentence compression<cite> (Sporleder and Lapata, 2005)</cite> , natural language generation (Prasad et al., 2005) and question answering (Verberne et al., 2006) .