http://www.wizards.com/default.asp?x=mtgcom/daily/mr165But there's more to artifacts than just how they're concepted on cards. In fact, when I started the Mirrodin Design Team (Tyler Bielman, Mike Elliott, Brian Tinsman and myself), the very first question I posed to the team was what are the qualities of an artifact. Here's what the team decided.
Interesting article on the design and development of artifacts.