Like sequence diagrams, collaboration diagrams are also interaction diagrams. Collaboration diagrams convey the same information as sequence diagrams, but focus on object roles instead of the times that messages are sent.  

In a sequence diagram, object roles are the vertices and messages are the connecting links. In a collaboration diagram, as follows, the object-role rectangles are labeled with either class or object names (or both). Colons precede the class names (:).

Each message in a collaboration diagram has a sequence number. The top-level message is numbered 1. Messages at the same level (sent during the same call) have the same decimal prefix but suffixes of 1, 2, etc. according to when they occur.