A 2D-PIR R_s(A,B) is a triple (t,xp,yp), where

• t is a topological relationship

• xp is the interval relationship between x-axis projections of A and B

• yp is the interval relationship between y-axis projections of A and B

Notes:

• approach extends naturally to nD-PIR

• R_s(A,B) ¬= R_s(A,B)   (there is a well-defined inverse)