I've got a really simple problem that I can't seem to fix. :-)

I'm trying to use a simplified model for a room planning problem. 

The planning entity is a Topic and the planning variables are Room and TimeSlot.

A Person is tied to a Topic as a moderator. 

Each Person can have multiple Topics as an interest.

The hard constraints are that a Person cannot be moderator in two Topics at the same TimeSlot and that there cannot be multiple Topics in the same Room at the same TimeSlot.

rule "conflictingModeratorInSameTimeslot"

    when

        $leftTopic : Topic($leftId : id, $leftTimeslot : timeSlot, timeSlot != null, $leftModerator: moderator)

        $rightTopic : Topic(timeSlot == $leftTimeslot, moderator == $leftModerator, id > $leftId)

    then

        scoreHolder.addHardConstraintMatch(kcontext, -1);

end

rule "multipleTopicsInSameRoomAndTimeslot"

    when

        $leftTopic : Topic($leftId : id, $leftTimeslot : timeSlot, timeSlot != null, $leftRoom: room)

        $rightTopic : Topic(timeSlot == $leftTimeslot, room == $leftRoom, id > $leftId)

    then

        scoreHolder.addHardConstraintMatch(kcontext, -1);

end

The soft constraint that I have a problem with is that a Person has multiple Topics as interests and I would like to penalize the Solution with the number of Topics in the Persons interests collection with the number of Topics that are allocated at the same TimeSlot.

Any ideas on how to go about this?

Regards,

Mats