Class-specific Token-level Loss The first modification we make is to pick a target entity class and modify ∆(y i , y) to have word-wise loss of tgt for false positives on the target class and loss of t gt for false positives on other classes.
let y j i be j-th element of sequence y i , we define ∆(y i , y) = j w j , where if y j i = y j tgt , if y j i = y j and y j = target class t gt , if y j i = y j and y j = target class Note that the target class in the above equation contains all the labels related to the target entity type; that is, if the target class is ORG, we consider B-ORG and I-ORG to be the related labels.