An empty slot object can be placed within a free slot in the same way as a card. Graphically, IltEmptySlot objects only differ from free slots by a dark grey label.

Empty slots can represent alarms and states graphically; however, their base representation cannot be changed. In other words, a state that would induce a change in the graphic representation of the object base is ignored.

You should associate an empty slot with a free slot if you want to manage this free slot in some way. Unlike an empty slot, a regular free slot is not considered a business object and cannot represent alarms or states by itself.