The books that encode some standardized Xbok are always named "The guide to the Xbok".
The actual BOK isn't supposed to have a concrete representation. It's not supposed to be standardized either, but standard organizations always ignore that part.
Well, literally the "state" as in what is the knowledge that everybody shares. We usually call that by something closer to "minimum common denominator".
What people usually call "state of the art" is the best knowledge that is reasonably well known. That is out of scope. If you take a look on this one, it's full of stuff that we knew not to use on the 20th century. This is typical.
The actual BOK isn't supposed to have a concrete representation. It's not supposed to be standardized either, but standard organizations always ignore that part.