Does your explanation have to exactly describe FTM's data model? Here's a (woefully-outdated) description of [The Master Genealogist's data model][1]. If it's only the sources/citations/media & "facts" entities you're describing, how about using the [Gentech data model][2] as a jumping-off point?   


  [1]: http://www.whollygenes.com/forums201/index.php?showtopic=381
  [2]: http://www.ngsgenealogy.org/cs/GenTech_Projects