id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
11837	Advanced key:layer checking in the validator	RicoZ	Klumbumbus	"Recently I came across a bridge with layer=-1 across a river with (implicit) layer=0. Surprisingly Mapnik and many other renderers draw it ""correctly"" - bridge above water despite obviously wrong layer. The JOSM validator does not produce any warning in this situation.

This may serve as an example, version 5 of the way if someone fixes it:
http://www.openstreetmap.org/way/28590490#map=19/45.86651/10.93736&layers=D

To detect this kind of error it could be necessary to model the vertical stacking by key:layer and compare that to the vertical stacking resulting from the algorithm described here:
   http://wiki.openstreetmap.org/wiki/Key:layer#Data_consumers
"	enhancement	closed	normal	15.09	Core validator		fixed