Mikael L. Littman showed in 1998 that with branching actions, the planning problem becomes EXPTIME-complete.[8][9] A particular case of contiguous planning is represented by FOND problems - for "fully-observable and non-deterministic". If the goal is specified in LTLf (linear time logic on finite trace) then the problem is always EXPTIME-complete[10] and 2EXPTIME-complete if the goal is specified with LDLf.