Touching outer rings

[wolfbert]

While touching inner rings are permitted in osm, how about touching outer rings?

JOSM sees this as an error, and it also cannot be handled by OGC conforming functions. These rings are sometimes used in an attempt to group neighbouring buildings (which can usually be expressed in some other way) and sometimes just plain unnecessary,

[joto]

Rules here are the same as for OGC/simple features. Outer rings are never allowed to touch in a line, in that case, just remove that line. Outer rings are allowed to touch in points (think of the figure 8), but the rules are more complex there.

[wolfbert]

It might be helpful to put this in the Wiki examples as well.