A potential UAWG position on @alt

Here's a stab at a potential UAWG position:

1. As a general rule, the UAWG has the expectation that markup languages 
will differentiate between any two cases in which a user agent would be 
expected to have different behaviors. (e.g., alt="" (by itself) can't 
simultaneously mean (1) aural browsers should attempt to find a value 
for the attribute from elsewhere and (2) aural browsers should ignore 
the image).

2. In deciding how to differentiate two cases that previously were not 
differentiated, backwards compatibility may not always be possible to 
maintain. (e.g. the signal for aural browsers to ignore an image might 
change from @alt="" to @decoration or something similar).

Cheers,
Jan