‘X zài Y wàibian’ (X is outside Y) (e.g., Qiú zài xiāngzi wàibian.) (The ball is outside the box): The compound position noun ‘Y wàibian’ (outside Y) refers to the outer surface of or the space projected outward from the outside of the reference object. The phrase ‘X zài Y wàibian’ (X is outside Y) expresses a spatial relation of exteriority whereby the located object is external to or occupies a space projected from the exterior of the reference object. Exteriority and interiority are semantically related by converseness. If X is interior to Y, then Y is exterior
to X, and vice versa.
Xiāngzi wàibian kǔn le hǎojǐ dào shéngzi.
(The box was bound on the outside a few times with string.)
Tā zài túshūguǎn wàibian xīyān.
(He was smoking outside the library.)
In (1a) the located object ‘string’ has direct contact or coincidence with the reference object ‘the outer surface of the box’, in (1b) the located object stays in the space projected outward from the exterior of the reference object ‘the library’.
 Loar, J. K. (2011). Chinese syntactic grammar: functional and conceptual principles. New York: Peter Lang.