inheritance between nodes in version scripts -- what is the pupose?

["Michael Kerrisk" <michael dot kerrisk at gmx dot net>]

Hello,

I'm confused around a detail of symbol versioning.  My difficulty is to 
understand the purpose of version node inheritannce in linker version 
scripts, as in the following:

VER_1 {
    ...
};

VER_2 {
    ...
} VER_1;

My question is about that very last line, which says that version node 
VER_2 "depends" on VER_1.  I take the word "depends" from the 'info ld' 
document, but that doc does not really explain the point (AFAICT), and the 
Sun "Linker and Libraries" guide does not dispel my confusion either.

So two questions:

1. What does "depends" mean?  

2. When is it useful to create "dependencies" using the above syntax, as 
opposed to just creating a set of independent version nodes, as in the 
following:

VER_1 {
    ...
};

VER_2 {
    ...
};

(A  hypothetical or real example for the latter question would be 
helpful.)

Cheers,

Michael