[josm-dev] Validator

[David Earl]

On 20/08/2008 10:24, Dermot McNally wrote:
> Layers exist to
> determine the drawing order of overlapping elements, nothing more.

... which rather violates the "don't tag for the renderer" maxim, yes?

There's a few cases where it can't be avoided, like where a bridge goes 
over another bridge in a complex intersection or by chance, as here:
http://www.openstreetmap.org/?lat=52.329752&lon=-0.192132&zoom=18&layers=B00FTF

But for the vast majority of cases, we ought to be able to tell without 
using layers.

For example,
- a waterway always goes under a road (except when marked as an 
aqueduct) irrespective of whether a bridge is marked or not.

- a bridge always goes over anything intersecting with it (other than 
possibly another bridge).

- a pond should always render on top of a park (indeed any area enclosed 
in another area could generally be assumed to render on top: even 
special cases like underground reservoirs still need to be rendered on 
top even if they are beneath a surrounding landuse area, say).

- linear ways (should) always render on top of areas, irrespective of 
any layering, POIs above those and all text on top.

David