The set of points in three-dimensional space.
(=> (And (Member ?X1 3d-Length-Space) (Member ?X2 3d-Length-Space)) (Quantity.Dimension (Distance ?X1 ?X2) Length-Dimension))
(=> (And (Member ?X1 3d-Length-Space) (Member ?X2 3d-Length-Space)) (Quantity.Dimension (Distance ?X1 ?X2) Length-Dimension)) (<= (Point-In $X 3d-Length-Space) (3d-Point $X)) (Inherited-Slot-Value 3d-Point Point-In 3d-Length-Space) (<=> (3d-Point ?Pt) (Point-In ?Pt 3d-Length-Space))