Please note that PMI, and there by M , are symmetric.
the expanded set of edges, F + , is now defined as F + = F ∪{(e, e ), (e , e) | e ∈ E + , e ∈ E, M e,e > 0} we augment the set of initial edges F with additional edges connecting entities in E + with entities in E such that PMI between the entities is positive.