[OSM-dev] JOSM: Several tags with same key

Matt Amos zerebubuth at gmail.com
Fri Apr 3 11:38:32 BST 2009

On Fri, Apr 3, 2009 at 7:24 AM, Stefan de Konink <stefan at konink.de> wrote:
> D Tucny wrote:
>> Then shouldn't that be two nodes? with the atm one having a layer=1 tag?
>> Similar to having a bar above a restaurant above a bank at the same
>> position but on different floors...
> There are better examples probably; what should a supermarket that has a
> post agency be talked like then?

one node with shop=supermarket, another with amenity=post_office? or
you could draw the building outline, tagged with shop=supermarket and
put a node inside it. or you could draw polygons for the floor area of
the supermarket and a separate polygon for the post office.

this sort of thing already exists for banks, but is tagged as
amenity=bank, atm=yes. you could easily adopt this for other types as
well: shop=supermarket, atm=yes.

while stefan is right (there is no technical reason why we can't
support duplicate tag keys whilst ensuring the tags themselves are
unique), the pragmatic approach is to recognise that most clients and
other bits of OSM software already use some sort of unique keyed map
to store tags. it makes it easier to explain to people what is going
on because there is one single amenity tag you can say things like "is
the amenity tag set to supermarket?", rather than "are any of the
amenity tags set to supermarket?". finally, while i don't doubt that
multiple keys would reduce some data duplication, i have yet to see a
compelling situation which can't be done without them.



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