[whatwg] ALT and equivalent representation

[Smylers]

Shannon writes:

> What about this as a possible solution?
>
> <img src="part1.png" altgroup="rating">
> <img src="part2.png" altgroup="rating">
> <img src="part3.png" altgroup="rating">
> <altgroup id="rating" value="3/5">
>
> I don't think this would raise any serious implementation issues as the  
> logic is quite simple;

What advantage does it have over Simon's proposal?

Simon's suggestion has the obvious advantage that it already works with
current browsers.

Smylers