A group consists of items and other groups. Groups cannot be empty. ARTIS allows nested groups, to any depth.
For the copy and cut operations, the selection status of the group elements determines what happens to the group itself.
A group gets copied if and only if at least one of its elements is in the selection.
A group gets cut if and only if all its elements are in the selection; the cut operation forces any groups that would be left empty into the selection.