It looks like it kinda is, I found this which describes the tables and it looks like a relational database as opposed to a name/value pair type database.
http://openvswitch.org/ovs-vswitchd.conf.db.5.pdf
But it looks like it might be different too, this mentions that the relationships are reversed compared to what one might think of as natural:
http://www.relaxdiego.com/2014/09/ovsdb.html
Here's the RFC for the management protocol
http://tools.ietf.org/html/rfc7047
So a relational database but not standard doesn't look like.