First, it makes no commitment to any kind of higher-level discourse structure over the discourse relations annotated between individual text spans.
while theory-neutral itself with respect to higher-level discourse structure, the PDTB invites experimentation with approaches to high-level topic and functional structuring (Stede 2012;Webber, Egg, and Kordoni 2012) or to hierarchical structuring (Mann and Thompson 1988;Asher and Lascarides 2003), as a resource for research aimed at a "data-driven and emergent theory of discourse structure" (Bunt, Prasad, & Joshi 2012, page 61).