[uwemaurer]

I didn't use Timefold but the predecessor Optaplanner, and I remember there were hard constraints which must always be true (eg one room can only be used for one meeting at a given time) and then there were soft constraints which were minimized (eg shorter distance is better)

so an optimization problem can then be described with a set of those hard/soft contraints

[ge0ffrey]

Yes! These days, to handle cases with more work than resources to do it, medium constraints are used a lot too (so hard/medium/soft constaints), to penalize the amount of unassigned work. Those are harder than soft constraints, but softer than hard constraints.