[OSM-talk] Relations not always brilliant

[Steve Hill]

On Tue, 8 Apr 2008, Lester Caine wrote:

> How DO we currently identify all roads in the UK, so
> that we don't end up with some of the simply silly links that the likes of
> Autoroute returns when asking for a location.
>
> We need a consistent UNIQUE index method that will allow all 'ref=M11'
> elements in the UK to be identified as that one element.

Why do we need them all to be identified with a single element?  You cite 
route planning as a reason but I really don't see why it is applicable - 
your route planner doesn't need to know that two bits of road with a gap 
between them are (administratively) the same road.

In fact, there are only 2 times a route planner needs to know about the 
road's ref or name:
1. When producing instructions ("Take the 3rd exit onto the M11")
2. As you cross from one way to another in order to determine if it is 
really a junction or just a continuation of the same way (you don't want 
it to tell you to "continue along the M11" at arbitrary points just 
because the way has been split there, and you might want to impose some 
kind of penalty for turning off the road to prevent the route from 
containing too many small turns).

Putting all of the separate bits of the UK's M11 in a single relation 
sounds about as silly as putting all the roads in the UK called "Station 
Road" in a single relation - they are separate roads and there is no good 
reason to treat them in any other way.

  - Steve
    xmpp:steve at nexusuk.org   sip:steve at nexusuk.org   http://www.nexusuk.org/

      Servatis a periculum, servatis a maleficum - Whisper, Evanescence