What is canon?

Because you know I love doing this to you guys. Lets discuss what is canon. do we take canon to be only what is written in AD, KH and begrudgingly Zebs guide, Or does canon include everything including the modules. Or do you consider canon materials to include everything TSR wrote about Star Frontiers (thus canon includes every TSR article in Dragon magazine, and everything in those endless quest books)?<br /><br />Or do you define Canon as anything produced officially by the company that bears the SF license in which case we have to..wait for it now...here it comes....accept what WOTC has published about SF as cannon too?<br /><br />So what is SF canon?<br />