On-line recognition of interval orders

The first one is optimal in time and space and recognizes the transitive closure of an interval order under the suborder hypothesis which means that we add a new element to the transitive closure of an interval order and test if the new digraph is always the transitive closure of an interval order. The second one recognizes the transitive reduction of an interval order in linear space and almost linear time under the linear extension hypothesis which means that we add a new maximal element to the transitive reduction of an interval order.