- Deal with the details of how to compose classes and objects to form larger structures.
- Allows both individual objects and composite objects to be treated uniformly.
- Compose objects into tree structures to represent whole-part hierarchies.
- The invariant information are separated into two classes leading to savings in terms of the memory usage and the amount of time required to create a large number of instances.
- Use sharing to support large numbers of fine grained objects efficiently.
- Access the contents of a collection without having any knowledge about the internal representation of its contents.
- Allows to add a operation to be defined across a collection of different objects without changing the classes of objects on which it operates.
