by When a Boolean is exposed to all terms of an alternative to which it does not belong, then it is necessarily false.
This technique is a special case of invariance; it is much easier to implement. It is used only on Booleans, whereas invariance also concerns empty cells.
The technique is also a generalization of intersection to Booleans. If the exposure applies in a single grid, then it is a case of intersection. The advantage of the exposure technique is that it applies to a Boolean duplicated in multiple grids without there being any intersection.
Let A be an alternative consisting of n Booleans. Any Boolean not belonging to A, exposed to the set of n Booleans of A, is false.
We need to identify alternatives formed by Booleans, starting with the simplest, those with two terms. Once an alternative is found, we look for Booleans outside this alternative that are exposed to all its terms. If we find one, then it is false.
Most of the time, the boolean being searched for is present in several copies on the grid.
Note that such a boolean can itself be part of another alternative.