Strict Weak Ordering

Binary Predicate
ie. compares 2 objects, returns T/F
f(x,x)  is false
f(x,y)  implies  !f(y,x)
!f(x,y)  and  !f(y,x)  implies x and y are equivalent (x == y)
x and y equivalent and y and z equivalent, implies x and z equivalent
x == y  and  y == z  implies  x == z