A greedy approximation algorithm based on \spider decompositions" was developed by Klein and Ravi for node weighted Steiner trees. This algorithm provides a worst case approximation ratio of 2 lnk, where k is the number of terminals. However, the best known lower bound on the approximation ratio is lnk, assuming that N P 6 6 DT I M En O(log log n) ], by a… (More)