Inference from the DOM

ARIA says multiple times:
"Not required if inferred by the DOM."

However, it doesn't say how the relevant properties are inferred from  
the DOM, so how is the author to know when an explicit property  
attribute is required? Please state in the specification how the  
properties are inferred from the DOM.

-- 
Henri Sivonen
hsivonen@iki.fi
http://hsivonen.iki.fi/