Define the role (role) of a group of objects that act on a specific task, such as the operation or use case collaboration diagrams may show static connections of objects suitable for the flow control function .
Assign roles (role) of a group of objects, to the specific task or operation, as well as the use case diagrams can display static connections collaboration of objects suitable for displaying the flow of control .
roles (role) of the group of objects against a job as well as operation or Use case collaboration diagrams may show static connections of the object is suitable for the display of the flow control