Collaboration diagrams are also communication diagrams. Collaboration diagrams give the same message as the sequence diagrams. But the collaboration diagrams depend on the object functions instead of the times at which the messages are sent.
The collaboration diagrams use the decimal sequence numbers as given in the diagram below to create it clear which operation is calling which other operation, although it may be harder to see the overall sequence. The top- level message is sequenced 1. The messages at the similar level have the same decimal prefix but different suffixes of 1, 2 etc according to when they happen.