$$\mathbb{N}$$
$$e t\;\;a l.$$

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

v

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

$$\mathbb{N}$$
$$\mathbf{j}$$  N. 

![0_image_3.png](0_image_3.png)

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

" Proceedings of the Fourteenth National Conference on Artificial Intelligence (AAAI-97)
References Journal of Logic Programming Proceedings of the Fourteenth International Joint Conference on Artificial Intelligence N