What does store.so module do?

Hi,

I noticed that when I build the broker (0.28 RC1), it builds following
modules (I enabled the linear store during the build):
$ ls /usr/local/lib64/qpid/daemon/
amqp.so ha.so legacystore.so linearstore.so store.so store.so.0.28
xml.so

I have no idea what does the store.so / store.so.0.28 do. When I don't load
the module neither the legacy store nor the linear store misses it. When I
load the store .so module alone, it also doesn't seem to do anything. Can
someone explain to me what does the store.so do?

Thanks Regards
Jakub