[Tagging] Reviving the conditions debate

Martin Vonwald imagic.osm at gmail.com
Wed Jun 13 17:15:53 BST 2012

Am 13.06.2012 um 17:45 schrieb Tobias Knerr <osm at tobias-knerr.de>:

> This means I didn't explain well enough. Let's update the example to
> make this more clear:
> maxspeed=80
> maxspeed:lanes = 60|80|80
> maxspeed:lanes?wet = ||50
> First step: Evaluate the conditions without regard for the semantics of
> the rest of the keys. "wet" is true, so this tagging changes to
> maxspeed=80
> maxspeed:lanes = ||50
> for the purpose of further evaluation. Remember: We did not take the
> semantics of "maxspeed:lanes" into account here, instead we relied on
> the ? separator to treat the front part of the keys in a generic way.
> This means that the maxspeed for the first lane will be 80 - there is no
> lane-specific value, so the road's general maxspeed is used. But it
> should of course be 60.

To me your evaluation is correct and your tagging is wrong. Any :lanes-tag specifies the values for all lanes for the basekey. If a lane value is omitted the general (i.e. non-lane) value applies. So the tagging should be:
  maxspeed:lanes = 60|80|80
  maxspeed:lanes?wet = 60|80|50
or using default values:
  maxspeed:lanes = 60||
  maxspeed:lanes?wet = 60||50

And finally: don't get me wrong! I really don't care a lot if it is a:b:c=x or a:b?c=x or whatever. As long as most people can live with it, use it and applications support it I'm fine with everything. I just throw my opinions in the ring, hope that many join and we find a good and accepted solution.


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