I had a quick view of the article and got a question. How it differs from this - http://codex.wordpress.org/Database_Description ? Yes, some brief explanations of the tables purpose, possibly for newbies. But I tend to be sure those who started to learn the WP database interiors are already familiar with some basic concepts and don't really need this. Codex article is pretty self explanatory and contains more useful information, like the types of database fields and their length, for example.