Composite

• A tree structure of simple and composite objects
• Compose objects into tree structures to represent part-whole hierarchies
• Let clients treat individual objects and compositions of objects uniformly

Component

• Declares the interface for objects in the composition.
• implements default behavior for the interface common to all classes, as appropriate.
• Declares an interface for accessing and managing its child components.
• (optional) defines an interface for accessing a component's parent in the recursive structure, and implements it if that's appropriate.

Leaf

• Represents leaf objects in the composition.
• A leaf has no children.
• Defines behavior for primitive objects in the composition.

Composite

• Defines behavior for components having children.
• Stores child components.
• Implements child-related operations in the Component interface.

Client

• Manipulates objects in the composition through the Component interface.