A notional proposal for a responsive images syntax

I'm aware that I'm late to this, but hopefully not too late. After reading
Matt Wilcox's brilliant summary of the state of responsive images, I was
moved to think of my own. It owes very large debts to many of the existing
proposals, but hopefully addresses some of the known drawbacks.

My full proposal is here:
http://www.broken-links.com/2012/06/14/a-notional-proposal-responsive-images-syntax/

In a nutshell, it works somewhat in the same manner as image maps, using
associated attributes. It can be used very simply as a like-for-like
replacement, but also expanded with user-defined variables. It's also
backwards compatible.

I've asked people to critique it and haven't encountered any major
criticisms so far, so am submitting it here for your review.

Even if this isn't viable, I hope it contributes to the debate.

Peter