[GRASS-dev] vector model question

[Markus Metz]

Does someone know what isles are *exactly* in the grass vector model? 
Isles in contrast to areas. I'm only interested in the definition of 
first-generation isles, not "an island in a lake on an island in a lake...".
I guess, an isle consists of one or more areas located within a larger 
area, and the isle does not touch the boundaries of the larger area. Is 
that right?

And maybe someone can explain to me the magic of 
dig_build_area_with_line()? I guess this function somehow determines if 
boundaries form an area (clockwise) or an isle (CCW). A wild guess.

Thanks,

Markus M