special characters in tags

[Tobias Knerr]

On 23.06.22 at 19:12, Martin Koppenhoefer wrote:
> in the German forum the question arose whether the “+” is an allowed char in tags:
> 
> https://forum.openstreetmap.org/viewtopic.php?pid=865766#p865766
> 
> Maybe the validator is overzealous here, or is generally agreed that some characters should not be used?

While the API accepts these characters, it is indeed good practice to 
avoid them in keys. (We even usually avoid spaces!)

Of course, data consumers need to be able to handle them because they do 
sometimes appear in the database. See e.g. these Taginfo stats on 
"problematic characters":
https://taginfo.openstreetmap.org/reports/characters_in_keys

Still, having to escape them in all sorts of contexts (not just as a 
programmer, but also as an experienced mappers using search and query 
tools, for example) can still be annoying and is a frequent source of 
various issues. So the validator is right to warn about it IMO.

Not sure if it's written down anywhere "official". The best I could find 
was this wiki section:
https://wiki.osm.org/Any_tags_you_like#Syntactic_conventions_for_new_tags