Second order template

A second order template, is a pattern which 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.

Examples

Third row

This pattern can be reduced to ziggurats:

Therefore the only forcing moves must lie in the overlapping area. However, the overlapping is alson non-forcing thanks to Vertical's (1) moves.

Usage

A first order edge template prove that a group is connected to the edge provided the player answer threats made to the connection. If the player wants to preserve the connection, the opponent can throw stones in the carrier 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.