While preparing time table through FET for our Institute, we are facing a typical problem. In some lab classes, we need to assign more than one labs to a particular activity as all required instruments for some lab courses are not available in one lab.
However, in FET, if we select, an activity has a set of preferred rooms, it allocates the activity in either of the rooms in that set. But we want to block both/all the rooms of the set for this particular activity.
I guess that can easily be done by providing an "OR"/"AND" option in the set of rooms constraint.
Please think of accommodating this in the next version of FET.
It is in the TODO, number 114 (see TODO file). Unfortunately, it is more difficult to make than it seems.
But you can solve the problem using dummy activities. Add an activity without students/teachers, same starting time with the real activity.