[Tagging] Discussion about Multivalued Keys

Matthijs Melissen info at matthijsmelissen.nl
Wed Jan 27 15:52:20 UTC 2016

Hi Colin,

Thanks for getting this discussion started. I agree it's fine to use
the proposal template also for proposals that are not about proposing
a concrete tag.

One thing to take into account in this discussion is that multi-valued
keys often move the problem to the data consumer. For that reason I'd
recommend to avoid them in many cases.

Take for example your example shop=supermarket, shop=bakery.
Independent of the exact way of tagging, using a multivalued tagging
scheme forces the renderer to make a decision between a supermarket
and a bakery icon. Basically, there is no possible way for the
renderer to support a multi-valued key here! The renderer might have a
rule that considers supermarkers always more important than bakeries,
or vice versa. But I think it's much more useful if the mapper decides
what's the main function, supermarket or bakery, rather than forcing
the renderer to make a choice.

-- Matthijs

On 27 January 2016 at 16:09, Colin Smale <colin.smale at xs4all.nl> wrote:
> Dear all,
> I have created a proposal page as a channel for constructive debate about
> the way forward. I hope you will all take a look and participate!
> Although this subject is a bit more than just a proposal for a new tag, I
> have used the same template. I will try and flesh it out a bit more in the
> coming days, but everyone is of course welcome to add their stuff.
> http://wiki.openstreetmap.org/wiki/Proposed_features/Multivalued_Keys
> --colin
> _______________________________________________
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> Tagging at openstreetmap.org
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