[OSM-talk] Where came the concept of ways, segments, nodes?

[Artem Pavlenko]

On 21 Mar 2007, at 09:54, Martijn van Oosterhout wrote:

> On 3/21/07, Mike Collinson <mike at ayeltd.biz> wrote:
>> May I ask some of our more long standing members where the concept  
>> OSM ways, segments, nodes came from?
>
> I don't know exactly (I wasn't there) but I think it came from looking
> at existing datasets which mostly work on the basis of polylines. A
> line consisting of multiple points. Now, that's terribly inefficient,
> so you seperate out the duplication and you get what we have now.

Perhaps, it came from a topological model - node, link , face ?
Do you mean inefficient for storing data? Can you explain more?

>
> In the process one inefficiency snuck in, namely that ways don't
> represent contiguous lines (they don't map exactly to polylines). Of
> we could enforce that in the API then we'd be set. The mapnik
> converter would probably like that :)
>

If you're talking about osm2pgsql converter it's doesn't matter.  
osm2pgsql creates planar graph for every bunch of nodes that are part  
of a way and creates *clean* geometries (as defined in Simple  
Features for SQL). It would be nice to avoid this step but this would  
require changing data model.


> Have a nice day,
> -- 
> Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/
>
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Artem Pavlenko
http://mapnik.org



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