Relation R (linear order):
R(a,a), R(a,b), R(a,c), R(a,d)
R(b,b), R(b,c), R(b,d)
R(c,c), R(c,d)
R(d,d)
R(0,x) x = 0, a, b, c, d, 1
R(x,1) x = 0, a, b, c, d, 1

Orthosupplement:
0 a b c d 1
1 d c b a 0

Candidates to fill: (0, a), (0, b), (0, c), (0, d), (0, 1)*, (a, a), (a, b), (a, c), (a, d)*, (b, b), (b, c)*