In the first two parts of this article, I spent lots of time and space blathering on about the advanced aspects of XML schema design, including such arcane concepts as complex datatypes, derivation by extension and restriction, and type redefinition. You were probably bored out of your wits, but you nodded your head wisely throughout out of politeness, and quietly hoped that that all that jargon was a prelude to something more interesting.
I'm sorry to tell you that it isn't. In fact, this third part is filled with even more technical gobbledygook, including such beauties as "primary key reference" and "selector". None of these terms are likely to make your day any sunnier - but hey, they'll sure teach you a thing or two about designing good schemas. If that sounds like something you'd like to learn more about, keep reading - it's time to take a little detour through the supermarket!