At boost 1.53 the library version was 10, however at boost 1.56 it has jumped to 11.

I have not seen any documentation/release notes about boost serialisation changes.
What has changed in boost serialisation to merit this change ?

The documentation in $BOOST_ROOT/libs/serialization/basic_archive.cpp  describes
the changes to boost library version, however it does *not* describe why it jumped
from 10 -> 11.

Any help appreciated.

Ta,
   Avi