We propose an efficient approach that avoids enumerating paths and instead models the underlying nodes directly.
we extend P e,e as the set of all category nodes included in any of the e → e paths, and define the aggregate metric as M e,e = γ e,e h∈P e,e π ee ,h M h , where {π ee ,h } are the relative weights of the categories such that h∈P e,e π ee ,h = 1.