Specifically, each label r in R corresponds to a candidate relation in which any considered pair (e, e ) of entities may participate.
since R cannot contain all relations that are implied in a corpus, we include in R an additional relation label "NA", which refers to any relation that cannot be regarded as the other relations in R. Any subset of R will be written as a {0, 1}valued vector of length |R|, for example, z, where each element of the vector z corresponds to a label r ∈ R. if and only if label r is contained in the subset, its corresponding element z[r] of z equals 1.