[Tagging] Deprecated features - highway=disused

[Craig Wallace]

On 20/12/2010 22:23, dies38061 at mypacks.net wrote:
> I came across http://wiki.openstreetmap.org/wiki/Proposed_features/Disused_road today.  I applied the proposal page template, indicating that the proposal had been obsoleted, as noted in the commentary on the page.  Looking at the tag info for highway (http://taginfo.openstreetmap.de/keys/highway), I see that there are presently 88 instances of highway=disused.
>
> Would you support addition of highway=discussed to http://wiki.openstreetmap.org/wiki/Deprecated_features as:
> * Date: (date of agreement here)
> * Old Key/Value: highway=disused
> * Suggested Replacement: highway=*&  disused=yes&  access=yes (no implied)
> * Reason: creation of general disused key
>
> The main problem I see with this proposal is the indication at key:disused that the use of the key implies access=no, which is not necessarily true in the case of a highway which is disused.  Could this be circumvented by the inclusion of the 'access=yes' recommendation in the suggested replacement?
>
> Thanks for considering this. --ceyockey (http://wiki.openstreetmap.org/wiki/User:Ceyockey)

I think using disused=yes is a very bad idea.
It will break all of the existing renderers/applications that don't know 
about that key, as they will show disused roads as normal roads, or use 
them for routing etc.
It means any routing application has to check for two different tags (or 
even more if you get things like abandoned=yes, construction=yes etc), 
before knowing whether the road is usable or not.

So I think disused=yes should be deprecated.
I think a better option would be a kind of namespace thing. eg something 
like highway:disused=primary etc.
Then that will be safely ignored by any applications that don't 
know/care about these roads.

There's a useful page here which summarizes some of this, and the 
pros/cons of different options: 
http://wiki.openstreetmap.org/wiki/Comparison_of_life_cycle_concepts

Craig