Composite structure diagrams depict the internal structure of a classifier, including its interaction points to the other parts of the system. It shows the configuration of parts that jointly perform the behavior of the containing classifier. 

A collaboration describes a structure of collaborating parts (roles). A collaboration is attached to an operation or a classifier through a Collaboration Use. 

Classes and collaborations in the Composite Structure diagram can have internal structure and ports. Internal structure is represented by a set of interconnected parts (roles) within the containing class or collaboration. Participants of a collaboration or a class are linked by the connectors. 

A port can appear either on a contained part, or on the boundary of the class. 

The contained parts can be included by reference. Referenced parts are represented by the dotted rectangles. 

Composite Structure diagram supports the ball-and-socket notation for the provided and required interfaces. Interfaces can be shown or hidden in the diagram as needed.