[Tagging] Interpreting "One feature, one OSM-object"

[Nathan Edgars II]

On Wed, Sep 22, 2010 at 7:19 AM, Andrew Harvey <andrew.harvey4 at gmail.com> wrote:
> Quite a number of times I've noticed a single way having the tag
> boundary=administrative (I assume having come from the Australian ABS
> import and being part of a larger relation marking some town or
> suburb) but also having waterway=stream (for example
> http://www.openstreetmap.org/browse/way/38128067).
>
> My interpretation of the "One feature, one OSM-object" suggestion
> would be that this is bad because the single way is being used for two
> different purposes (representing a river, and representing an
> administrative boundary). Because then you don't know which tags refer
> to the river feature and which to the administrative boundary feature.

I think "one feature, one object" is usually used in the other
direction: you don't tag the boundary name=x and also put it in a
boundary relation with name=x. You don't put a fast_food node in the
middle of a building that only holds the fast food place; you put the
fast_food tags on the building (or, even better, the parcel of land
owned by the company, which includes the parking lot). Having a
boundary relation and a node at the city center violates this
guideline, but is a valid exception because the node carries other
information about where the city center is.

As for the specific question, I would say that if the boundary is
defined by the natural feature, it's probably OK to use one way. For
example, http://www.openstreetmap.org/browse/way/78384443 is legally
defined as "...to the water's edge of Little Lake Conway; thence run
southeasterly along said waters edge to a point of intersection..."