Multiple objects in a .obj

I have a question about storing multiple objects in a Wavefront .obj file, as the docs I have read aren't too clear on the subject. Does each sub-object have its own set or vertices, or are they shared within the entire file? For example:

# style 1
o object_1
v 0.0 0.0 0.0
v 1.0 0.0 0.0
v 1.0 0.0 1.0
v 0.0 0.0 1.0
f 1 2 3 4

o object_2
v 0.0 2.0 0.0
v -1.0 -1.0 0.0
v 1.0 -1.0 0.0
f 1 2 3

# style 2
v 0.0 0.0 0.0
v 1.0 0.0 0.0
v 1.0 0.0 1.0
v 0.0 0.0 1.0
v 0.0 2.0 0.0
v -1.0 -1.0 0.0
v 1.0 -1.0 0.0

o object_1
f 1 2 3 4

o object_2
f 5 6 7

My maps are designed in a way that requires use of .objs with multiple objects, so I need to figure this out before I can continue. Any help is appreciated.