[Tagging] Implied oneway tag for highway=*_link, wiki edits

Liz edodd at billiau.net
Thu Nov 26 19:56:08 GMT 2009

On Fri, 27 Nov 2009, Tobias Knerr wrote:
> All of these tags were previously documented to imply oneway=yes. Now
> only the page for highway=motorway_link still contains that implication.
> Generally, I don't think it's acceptable to change the definitions of
> tags in this way. Maybe you believe that these implications didn't
> actually make much sense or weren't implemented consistently. But they
> were documented in the wiki for quite some time, so it's inevitable that
> at least some mappers and applications used them. A change like this
> should be preceded by at least some discussion, and we should try to
> reliably inform application developers. There also needs to be a way of
> of how to deal with existing data based on the old documentation.

and when the comment in the history from 21 June is read it says
(This won't break any ways, because 1. nobody (approximately) uses this for 
routing yet, 2. assuming they're 2-way in a routing app is potentially 
dangerous anyway.)

so the person who changed this couldn't think very far into the future

or this comment from 10 November
(Implicit oneway discourages users from giving definitive tagging. Implicit 
defaults are also liable to change.)

which is called a "self-fulfilling prophecy" in English.

however the comment from 5 September
(Changed 'oneway=yes' to 'oneway=no' to make consistant with 
(http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing#Oneway), mapnik, 
osmarender, and converters to garmin)

simply changed a default because the renderers didn't cope.

I don't recognise any of the names as being involved in the mailing list.
I do support some discussion rather than edit wars on the wiki.

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