[OSM-dev] Proposal: Make relations ordered

Richard Fairhurst richard at systemeD.net
Mon Mar 17 11:02:43 GMT 2008

Jo wrote:

> OK, fair enough. I hope JOSM and Potlatch get around to implementing it
> sooner rather than later then. It's rather annoying to carefully define
> a route relation, knowing that it can be blown apart by people who
> remerge the parts or split them in other ways. I tested this and it
> gives undesired results at the moment.

To be honest the thought of relations getting ordering fills me with  
dread. Potlatch is only just about to get relations support (thanks  
entirely to Dave Stubbs) in 0.8; the thought of having to redesign it  
and add a load of crap to handle splitting/merging/whatever doesn't  
exactly fill me with joy.

Plus there's a more general worry that with this, and with layers, and  
whatnot, we're moving away from "simple is good" to "let's have a  
super complex data model that covers all eventualities".

AIUI the problem you mention above is nothing at all to do with  
ordering. It's because the editors don't make it sufficiently explicit  
what is part of a route relation, and what isn't. If the editor  
highlights such routes in a different colour (as Dave's excellent code  
for Potlatch does) then users will _see_ when they split or merge  
wrongly, and modify their behaviour accordingly.

Similarly I don't see why Frederik's initial ribbon-like loop  
needs to be solved by ordering. One of the most frequently cited use  
cases for relations is turn restrictions. Surely this is nothing more  
than a non-mandatory turn restriction?


More information about the dev mailing list