[Tagging] Defaults (Re: sidewalks and tagging for the renderer)

[Nathan Edgars II]

I think we're talking about two different things here.

(a) An editor (program) automatically applying tags to an object. This 
is bad, because we don't know whether the mapper has specifically 
verified this, or whether it's just being assumed and may be false.

(b) Tags on an area that specify defaults for objects within the area, 
to be processed by the end-user who downloads the OSM data. This could 
be good. For example, in Florida, whether bicycles are allowed on 
sidewalks is a matter for the local government to decide. So it would be 
useful to specify that footway=sidewalk implies bicycle=no inside city 
limits, unless otherwise overridden by a tag on the sidewalk way. And 
you could still set bicycle=no on the ways if you want.