Draw and gradient opacity

Hi,

obviously I'm working with gradients at the moment  :-)   and I'm in 
need of a code pointer again.

I've created a rectangle in Draw (manually - no svg import this time), 
filled it with a linear gradient with a constant 50% opacity and saved 
the file as fodg. Then I saw that opacity is stored at two places in the 
file:

1. in the gradient definition (draw:start-intensity="50%" 
draw:end-intensity="50%")
2. in the rectangle style (draw:opacity="50%")

If I remove it in the rectangle style and re-open the fodg file the 
rectangle isn't filled transparently anymore, i.e. the opacity in the 
gradient definition is ignored. So my question is: Which code is 
responsible for reading fodg files (to check if start-intensity and 
end-intensity are processed at all) and which code does the painting?

Hope that I've used the correct terms...

Christina