At our company, we are using four token versioning concept. It's something like a.b.c.d kind:
(major).(feature).(revision).(bug/refactoring)
It's related with issue types which we use in our development life cycle. We can track what has done or changed between two following versions at a glance. By comparing two following version numbers you can identify number and types of issues done.
For more information, full documentation is here.
