

![0_image_0.png](0_image_0.png)

The next step is done for F4 feature. PRG algorithm determines that F4 is a one-feature rule reduct for x 4 . Then pruning process is begun and the tree nodes F2F4, F2F3F4, F1F4, F1F3F4, F1F2F4, and F1F2F3F4 are pruned. Because these features include F4 feature and they are redundant rule reducts.

![0_image_1.png](0_image_1.png)

It is told above that the PRG traces the tree in-order direction. After finding rule reduct for F4 feature, it is expected that the algorithm will begin to search for F3F4 node. But since F3 is a one-feature rule reduct, the algorithm passes the right child. Then the right child of the F2 ,
F3 will be searched, but it is also pruned so this node and its right child F2F3F4 are passed. The next node is F2F4 , but by reason of one-feature rule reduct for F4 , it has been also pruned and it is passed. Finally in execution queue the node F1F2 is searched whether it is a rule reduct or not. It is not rule reduct, hence the algorithm does not make any process for this feature couple. The result of execution is shown in Figure 4.5. The other six nodes are not searched by PRG because they have been all pruned.

![0_image_2.png](0_image_2.png)

