Object instances connected by links. Instance of the corresponding class diagram. No multiplicities. Underlined class name and object name; class name may be elided; anonymous object name possible Separator between object and class names: ``:''.
Roles are parts of collaborations. They are represented like classes with role name followed by colon followed by type. Not underlined. Instances are underlined and shown with optional name, followed by optional slash, followed by list of roles, colon and list of types.