For instance, the popular Penn Discourse Treebank (PDTB) benchmark data (Prasad et al., 2008) was annotated by first inserting a connective expression (i.e., implicit connective, as shown in the above example) manually, and determining the abstract relation by combining both the implicit connective and contextual semantics.
the huge performance gap between explicit and implicit parsing (namely, 85% vs 50%), as well as the human annotation practice, strongly motivates to incorporate connective information to guide the reasoning process.