[OSM-dev] Source tag on each node

[Wyo]

I've just realised that rather many nodes have their own source tag, even if 
they are just part of a way with identical tag. So I guess a rather large part 
of the data consists of these source tags. While this isn't a problem for files 
(thanks to compression) it enlarges the database quite a bit.

Are these tags really necessary or could they be remove as long as the way has a 
source tag? Could anybody provide an estimate how much space reduction could be 
gained? Could anybody create a report on how many nodes have identical tags as 
their way?

Wyo