[OSM-dev] Proposal: Make relations ordered

Dave Stubbs osm.list at randomjunk.co.uk
Mon Mar 17 12:21:28 GMT 2008


On Mon, Mar 17, 2008 at 11:02 AM, Richard Fairhurst
<richard at systemed.net> wrote:
> 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.

The main problem with implementing ordering to the relation support in
Potlatch would be actually supporting either changing or showing the
current order. JOSM treats relations as a separate object and only
lets you edit them through a dialog box, but the new Potlatch support
basically adds relations as an extended feature of a way/node that you
can share.


>
>  [snip]
>
>  Similarly I don't see why Frederik's initial ribbon-like loop
>  (http://lists.openstreetmap.org/pipermail/dev/2008-March/009389.html)
>  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?

It's possibly slightly more than that, for instance if you're trying
to write software to 'follow' the route, you want to know that the
restriction is mandatory for that route, and also the idea of a
"non-mandatory restriction" is a bit hard to get through my brain :-).
But you can still model it without ordering using more relations...
maybe route_restriction, or an extra on_route role for the normal
restriction.

Dave




More information about the dev mailing list