Compromised Diagonal
Black's diagonal play here is regarded as 'compromised' by the presence of either marked White stone.
The point with the marked Black stone on it, or a, is good for Black's eye shape - imagine Black now at b.
The terminology is attributed to Victor Chow.
This is a 3-4 point, high approach, inside contact, solid connection joseki. Note how the diagonals are compromised by
.
Here, is a common probe, leaving Black with weaknesses at a and b. As Black can choose to defend only one of them, White can then decide the follow-up moves.
See also: