[OSM-dev] HEADS UP osmosis pgsql schema users Was: psql osmosis simple shema / smallint out of range

[Frederik Ramm]

Hi,

Andy Allan wrote:
> Should we restrict the maximum number of relations|ways|nodes that can
> be *direct* members of a relation? I don't mind cascading relations,
> but 39000 direct members of a single relation might casue issues too.

I tend to say yes, limit it in some way.

People are starting to get very creative with relations, which I partly 
like and partly view with skepticism.

Relations are meant - at least I thought that's what they were for - to 
model strong relationships between objects, like: The following 
buildings together form the university campus, or: you may not turn from 
this road into that, or: these 53 ways together form the Golden Jubilee 
walk. These are important uses which relations are needed for.

Increasingly, and I believe this is born from unreflected Wikipedia 
customs being applied here, people make "collections" or "categories" 
using relations, for example "cycle network North-Rine-Westphalia" 
containing every cycle route in that part of Germany, or another 
relation containing every German Autobahn, or one containing all 
McDonald's restaurants.

I fear the day is not far when someone will start neatly categorizing 
POIs into relations like "UK bakeries", "railway stations in Europe" or 
other niceties.

This does not make sense; retrieving all McDonald's restaurants or all 
Autobahns in Germany is one OSMXAPI query, it does not require a human- 
maintained relation (that only makes things harder for newbie 
contributors). Anything that *can* be modelled without a relation should 
be modelled without one. If you want to flag all historic dome-roofed 
railway stations then, at least that would be my recommendation, please 
simply tag them "building_type=historic;dome-roofed" or something, 
instead of making a relation to which you add the object.

If the only thing that connects two objects is that they have a common 
property, I'd say a relation is not the way to model that.

That being said, I'd say there is merit in connecting all the ways that 
form a trans-country motorway into one relation, and what with our 
split-way-mania that may easily amount to a few thousand pieces...

Bye
Frederik

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