[OSM-talk] Advanced relationships

[Robert (Jamie) Munro]

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Nic Roets wrote:
> On 6/13/07, Robert (Jamie) Munro <rjmunro at arjam.net> wrote:
>> Example uses:
>> * Turn restrictions between segments
> 
> Currently we can do pretty sofiticated stuff with oneway=yes and ways
> crossing each other with or without an intersecting node. Any examples
> of a particular requirement that you want to address ?

Where there is a no right turn at a crossroads. You can go straight on
or left, and people starting from the left can go to the right (which is
straight on for them), but you can't go right because that would mean
crossing dangerous oncoming traffic.

>> * Place is in place between nodes (with a value if it has a special
>> significance, e.g. it's the capital)


>> * 3 ways: Road A, Railway B, Bridge C; two relationships A "is on" C, B
>> "is on" C where a road and railway share a bridge.
> 
> On some blog I've seen a similar requirement, but I can't see why it
> would be important to indicate this. Is it purely cosmetic (i.e.
> rendering) ? If yes, we should be considering full blown 3D virtual
> reality. Now that will look nice, but it will also slow the mapping
> pace to a real crawl.

A map should indicate obvious landmarks unambiguously. It doesn't have
to be full blown 3D to do this, but it does need to show 1 object as 1
object, not two objects.

>> * Way "is border" of country, county or city node. Every county border
> 
> I still don't know how to survey that information. Sometimes it's
> obvious where a county or a suburb ends, e.g. 2 signs either side of a
> big road. In that case it will also be obvious where the border is for
> anyone who look at the map.

True, it's not always easy to tell where the border of a county is, but
if I do happen to know that one side of a river or road is one county
and the other side is a different county, how else should I mark that in
the map?

> We need to become more like WikiMedia, namely it must be easy for
> anyone to add or change stuff. But if there are relationships all
> over, it simply wouldn't be the case.

I don't follow. With a good editor, why would relationships be hard?
There's no compulsion on people to enter them, any more that there is
compulsion on people to enter anything else at the moment.

Robert (Jamie) Munro
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