For practical or organizational reasons (such as Conway’s law), complex planning problems are often broken down in multiple stages. A typical example is train scheduling, where one department decides where and when a train will arrive or depart, and another departments assigns the operators to the actual train cars/locomotives.

Each stage has its own solver configuration (and therefore its own SolverFactory). Do not confuse it with multi-phase solving which uses a one-solver configuration.

Similarly to Partitioned Search, multi-stage planning leads to suboptimal results. Nevertheless, it may be beneficial in order to simplify the maintenance, ownership, and help to start a project.