[Tagging] Simplify building:part areas

[Tom Pfeifer]

On 18.08.2017 02:30, Clifford Snow wrote:
> On Thu, Aug 17, 2017 at 4:12 PM, Javier Sánchez Portero <javiersanp at gmail.com 
> <mailto:javiersanp at gmail.com>> wrote:
>     * In the wiki [1] says that the outline should be tagged with building:levels and height, but
>     this, if the parts cover the whole outline, is a duplication since these tags will always be in
>     some of the parts. Could I delete the part(s) whose labels match those of the outline?
> 
> If you use a multipolygon, then the multipolygon would contain the levels and height.

The building outline represents the "footprint" of the building on the ground, and provides all 
non-3D properties such as building type (e.g. building=apartments), address, overall height, etc.
Thus it provides backward compatibility for a data consumer who does not want to evaluate building:part.

If e.g. the lower floors of the apartment building is wider than the upper floors, you can tag the 
outline with both, building=apartments and building:part=yes and the appropriate 3D-properties, and 
the narrower upper floors with building:part=yes and 3D-properties, but without building=*.

tom