[OSM-talk] superways as relations ?

[Dave Stubbs]

On Wed, Aug 6, 2008 at 5:47 AM, Robin Paulson <robin.paulson at gmail.com> wrote:
> 2008/8/6 Ben Laenen <benlaenen at gmail.com>:
>> On Tuesday 05 August 2008, Karl Newman wrote:
>>> Sounds like you're looking for this:
>>> http://wiki.openstreetmap.org/index.php/Relations/Proposed/Segmented_
>>>Tag
>>
>> Segmented tags doesn't solve data duplication for dual carriage ways, or
>> a set of roads with lots of cul-de-sacs with the same name, and similar
>> situations.
>
> is there any reason why the data model has to have ways which are
> single direction and linear? by which i mean, why can't a single way
> be branched in shape?
>

We used to have Nodes (as now), which were joined together by Segments
which just connect two nodes and had a direction. Ways were made of a
collection of Segments -- the API preserved the order of the Segments
in the Way but did not impose any rules about the Segments being
connected to each other. This allowed unconnected, branched, and
"unordered" ways to be formed. I'm sure if you google for "unordered
ways" it will still show up numerous discussions. Sometimes renderers
found it tricky to place labels along them, the branches being a
little confusing, and a few reversed segments down a way caught out at
least one of the renderers for quite a while. Also there were some
very ambiguous one way roads, as the "direction" of the way was
determined by the order of the segments, or maybe the direction of the
segments... no-one was ever quite sure.

Anyway, segments became not very useful for anything so were removed
at the same time relations got added.

So the answer to your question is that with relations you could do
branched stuff, but I wouldn't be surprised if people tell you ur doin
it wrong.

Dave