The object diagram below instantiates the class diagram, replacing it by a concrete example. Each rectangle in the object diagram corresponds to a single instance. Instance names are underlined in UML diagrams. Class or instance names may be omitted from object diagrams as long as the diagram meaning is still clear. Sequence diagrams Class and object diagrams are static model views.
Interaction diagrams are dynamic.
They describe how objects collaborate. Sequence diagrams are organized according to time. The time progresses as you go down the page. The objects involved in the operation are listed from left to right according to when they take part in the message sequence. Below is a sequence diagram for making a hotel reservation.