Second order template
A second order template is a template that guarantees a connection even if the opponent is given a free move at the beginning. Put another way, a second order template is a pattern in which an intrusion is not a forcing move. A pattern can be proved to be a second order template by showing that every possible intrusion preserves at least one first order template.
Contents
Examples
Second row
Third row
This pattern can be reduced to ziggurats:
Therefore, any potential forcing moves must lie in the overlapping area. However, the overlap is also non-forcing, thanks to Red's moves A and B.
Usage
A first order edge template proves that a group is connected, provided the player answers threats made to the connection. If the player wants to preserve the connection, the opponent can intrude into the template's carrier and play stones that will later serve as ladder escapes. Such moves belong to the category of double threats. Recognizing second order edge templates helps to know whether an area is safe or might be subject to such double threats.
