Collaboration diagrams are another means for representing the interactions and relationships between objects. Unlike sequence diagrams, however, they do not focus on the timeline of interaction, but on the structural connections between collaborating objects. Of central interest are the messages and their intent, when creating a collaboration diagram. The chronological order of messages is represented by numbers preceding each message.
Objects - In collaborations, objects represent different roles - these are specified as Classifier Roles in Poseidon for UML.
Associations - Associations illustrate the connections between collaborating objects. Messages are then placed along them.
Messages - Just like in sequence diagrams, messages are used to describe the interaction between objects. The numbers in front of the given names represent the chronological order of messages. Using the corresponding buttons in the toolbar of the Properties tab, you can specify an action for the message, and you can change the direction of the message .