F a c t                .             |
|              /     Abstraction     \                 .              |
|             /       *       *       \               .               |
|            /      *           *      \             .                |
|           /     *               *     \           .                 |
|          / C a s e             C a s e \         .                  |
|         /   *                       *   \       .                   |
|        /  *                           *