(bn) A new bn is generated from the initial bn reduced to the
targetted nodes indicated in 'ion' and the parents of these nodes.
Independent uniform distributions are given to the parents AND AT THE
SAME TIME THEIR OWN RELATIONSHIPS ARE DELETED. For some argument
about this practice, see the DETAILS section of function study8nd.
To give an example, the graph (A->B; A->C; B->C) will result into (A->C; B->C) if (C) is the targetted node.
The original bn.
The definition of the nodes (iin or name vector)
The resulting bn