It belongs to a class of directed hypergraphs (Gallo et al., 1993), where each hyperedge e consists of a single designated parent node (head of e) and an ordered list of child nodes (tail of e).
our segmental hypergraph consists of the following 5 types of nodes: • A i encodes all such mentions that start with the i-th or a later word • E i encodes all mentions that start exactly with the i-th word • T k i represents all mentions of type k starting with the i-th word • I k i,j represents all mentions of type k that contain the j-th word and start with the i-th word • X marks the end of a mention.