Review of notes and insights from the AGENCY talk at HXWG last week.  Here is the wiki page 

Rumsfeld Structure to scope  "Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns—the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tends to be the difficult ones.^{[1]" (Source: Wiki)}