Driver OVO is used for drivers to report to agent. It contains the
layered objects as well as the functions in order to operate the
DB. The design of driver OVO is reference to:
https://docs.google.com/document/d/
1XLQtvyGJeEgo3ztBQiufWLF-E7S7yGLaYrme8iUPtA0/edit
Change-Id: I997a251673e1b7cfdb035d58889781c6943b3db7