STELLA [Sebastia, Onaindía, MarzalSebastia et al.2001] uses a forward heuristic search architecture, but with the modification that plans are built using landmarks [Porteous, Sebastia, HoffmannPorteous et al.2001]. The idea is to identify key states in the path of a plan before planning begins and then to use these as ``stepping stones'' to progress from the initial state to the goal state.