Referring to FIG. 4, for example, there are paths from node A to nodes G and K other than through C, but there are no paths from A to nodes H and J other than through C. Therefore, links 430 are inserted from A to H and from A to J, but not from A to G nor from A to K. [0190] Remove p from the parents vector of pi, and remove pi from the children vector of p (step 1084).