UX vs. XD

My colleague Travis Stiles ponders the distinction between UX and XD:

Certainly the practice of UX or XD can vary and anyone calling themselves an “XD” can practice user-centered design, but my goal here is to define the implicit value and meaning in both terms and how that might affect the use and context of each.

Its got my brain turning on something I've been thinking about since I've heard the term "experience design." I've always thought about XD in terms of art making and installation work, which for many artists puts the cart before the horse. There's an idea or aesthetic you'd like to explore and while participation is key in that experience, "getting it" isn't necessarily the primary goal. Definitely a useful distinction that I'm looking forward to hearing more about!