Use-cases for version ranges?

[cowwoc]

Can someone please explain why modules need to be able to specify version
ranges for dependencies? I believe OSGI allows the specification of version
ranges while Maven allows the specification of individual versions.

The only thing that comes to mind is when module C depends on A and B, A
depends on log4j 1.0, and B depends on log4j 1.1. What does C do? Is this
the main use-case for version ranges?

By the sound of it, this is a trust model where developers are told that
log4j 1.x won't break compatibility so they depend on that range without
actually testing against each version (newer versions may be released after
their own software). I question whether such a mechanism is better or worse
than depending on individual versions which may be overridden at a later
time (a la Maven). On the one hand, you don't need to release a new version
of the application each time a dependency is updated. On the other hand, no
one is actually running tests to ensure that the versions are really
compatible.

Is there a way to get module A to see log4j 1.0 and module B to see log4j
1.1 (using separate ClassLoaders)?

Thanks,
Gili

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