HAS-VALUE is a way to state that an instance has a value on some slot. Its third argument is a single value; one may use HAS-VALUE repeatedly for each value of a multiple-valued relation.
For example, (HAS-VALUE i R v_1), (HAS-VALUE i R v_2) means that slot R applied to domain instance i maps to values v_1 and v_2. In other words, R(i,v_1) and R(i,v_2) hold.
There is no closed-world assumption implied; there may be other values for the specified slot on a given domain instance.
(Nth-Domain Has-Value 2 Binary-Relation) (<=> (Has-Value ?Instance ?Binary-Relation ?Value) (And (Binary-Relation ?Binary-Relation) (Holds ?Binary-Relation ?Instance ?Value)))