Optiplan: Unifying IP-based and Graph-based Planning
  The Optiplan planning system is the first integer programming-based planner that successfully participated in the international planning competition. This engineering note describes the architecture of Optiplan and provides the integer programming formulation that enabled it to perform reasonably well in the competition. We also touch upon some recent developments that make integer programming encodings significantly more competitive. 
S. Kambhampati, M.H.L. van den Briel
cs.AI