Sentence:  To save the <WSD>treeness</WSD> of discourse structure – and with that the supplied computational advantages – Egg and Redeker (2008) argue that many apparent crossed dependencies reflect anaphoric relations on the level of discourse cohesion…. They opt for a pure tree structure for discourse relations, keeping anaphoric relations apart. 
Meaning of the word marked with <WSD> tags:  The condition of being a tree; acyclicity and connectedness.