[rules-users] how to get first and last element of list of facts?

Hi, I need to plan some tasks within a nr of timeslots. Until now a task was always done within the period of one timeslot and I could validate my rules since a task has a planning variablegetTimeSlot/ setTimeSlot. Now requirements have changed and a task can take more than one timeslot to complete. What is the best way to validate that the task is not started in a timeslot that would end the task after the last timeslot? - Timeslots are always equally long (for example a week). - All timeslots in the list of timeslots are sequential (no gaps). So if I have a list of timeslots W18, W19, W20, W21 and I have a task taking 3 TimeSlots to complete, it should start in W18 or W19. Should I create a single planningRange fact, holding the first and last slot? Any directions would be appreciated. Regards, Michiel Vermandel   ----------------- http://www.codessentials.com - Your essential software, for free! Follow us at http://twitter.com/#!/Codessentials