WanMil, Thanks for the explanation. It seems that this process is needed, at least in part, to make sense of incorrectly tagged data. There certainly will always be incorrectly tagged data, which programs such as mkgmap and renderers will have to interpret. But is there any way that the deleted tags could be retained in some form for access in the style files? Perhaps they could be re-named along the lines of 'deleted:name=High Dam' .
Certainly yes. But I don't see the requirement for it - it has some drawbacks (memory requirement). In your example the outer way is tagged with landuse=reservoir and natural=water. You want to have two polygons - one for the mp (natural=water) and one for the way (landuse=reservoir). Why do you need the two items? Doesn't natural=water and landuse=reservoir tag exactly the same thing? WanMil