As noted earlier, our definition of profile density depends on identifying a suitable set of ancestor nodes of the concept nodes in the profile: the aggregate distance of the ancestors to the profile nodes indirectly indicates the degree to which the profile nodes are spatially clustered close together.
given a profile P, we need to find A, the set of nodes that are ancestors of the profile nodes d ∈ P. (The nodes a ∈ A correspond to the hollow triangles indicated in Figure 8 and Figure 9.)