[Tagging] Discussion about Multivalued Keys

Colin Smale colin.smale at xs4all.nl
Wed Jan 27 17:40:40 UTC 2016

I think refs on highways is definitely one of the cases where ordering
might be significant in real life, as the shields next to the roads and
on overhead signs will be in a particular order which may be said to
infer some kind of weighting or priority to the largest, or topmost,
signs. But there other cases, with different tags, where ordering is
arbitrary and 1-2 is totally equivalent to 2-1. Which is why the syntax
at the level I am seeking to discuss now, should not force the list to
be interpreted as ordered - that depends on the key and we can have that
discussion (also about whether the values are actually ordered in real
life!) later.


On 2016-01-27 18:16, Bryan Housel wrote:

> Hmm, I think the semicolon separated tags are necessarily ordered.  Jochen has it a bit wrong in the blog with his example about coincident highways. 
> For example US 1-9 by NYC is tagged `ref=US 1;US 9`.  It would be a mistake to treat that as equivalent with US 9-1, as it's definitely not called that nor signed that way:  http://www.openstreetmap.org/way/51509994 
> I'm sure there are other examples of this, where the ordering of coincident highway refs would look totally wrong if reversed. 
> On Jan 27, 2016, at 11:36 AM, Frederik Ramm <frederik at remote.org> wrote: 
> Hi,
> On 01/27/2016 04:09 PM, Colin Smale wrote:
> 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! 
> One thing that I would like to see discussed is ordering. For example in
> the semicolon word, is "shop=a;b" the same as "shop=b;a" or does the
> former mean that it is an "a" with attached "b" and the latter mean that
> it is a "b" with an attached "a"?
> If a;b is identical to b;a then having both is of course a major pain
> and would shift a lot of preprocessing work on tools like taginfo.
> On semicolons, also see
> https://blog.jochentopf.com/2013-09-23-semicolons-in-osm-tags.html
> Bye
> Frederik
> -- 
> Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"
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