[OSM-dev] API 0.7+: Split node concept?

Frederik Ramm frederik at remote.org
Tue Oct 12 21:19:15 BST 2010


Hi,

Chris Browet wrote:
> I am wondering (I wonder a lot lately ;-)) if some have already given a 
> thought to the fact that nodes actually represent 2 different concepts 

Yes, this is something that has been discussed on and off for at least 
two years. I know because we mentioned in the first edition of our OSM 
book ;)

Of course the "node" element would have to be kept not only for POI 
nodes but also for topology nodes (where two ways meet).

Having geometries in ways would be much more traditional-GIS-like and 
would simplify many things. However your suggestion mixes in-way 
geometry with geometry by reference to nodes; and it has to because 
otherwise you lose topology. But this means you don't get the full 
advantages of either.

A big potential problem I see is promoting and demoting nodes - you 
select and tag a "point" in a way, thereby creating a node; you later 
remove the tag from the node, thereby deleting a node. You let a road 
and a forest boundary share geometries, thereby creating proper nodes 
for each shared coordinate; you split them apart, deleting the nodes and 
creating two sets of points-in-ways.

I see the basic idea but it all seems a but uneven to me, even ugly to 
implement.

Most of the positive aspects for the consumer could probably be achieved 
by producing a kind of augmented planet file and diff, where internally 
you still have nodes and ways as ever, but all <nd> objects are extended 
with a lat and lon attribute. If the node is untagged it will not be 
present in the nodes section of the file; if it is tagged it will be 
present.

This would be API version independent.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"



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