A relation R is an total-order if it is partial-order for which either R(x,y) or R(y,x) for every x or y in its exact-domain.
(<=> (Total-Order-Relation ?R) (And (Partial-Order-Relation ?R) (=> (And (Instance-Of ?X (Exact-Domain ?R)) (Instance-Of ?Y (Exact-Domain ?R))) (Or (Holds ?R ?X ?Y) (Holds ?R ?Y ?X)))))