[Tagging] My "weirdly unnatural aversion to relations"

Bryan Housel bhousel at gmail.com
Sun Sep 30 03:00:09 UTC 2018

> On Sep 29, 2018, at 6:56 PM, Paul Johnson <baloo at ursamundi.org> wrote:
> I honestly don't understand why, ten years since it's introduction as OSM's third basic primitive, there's still this weirdly unnatural aversion to relations, even though they're quite a powerful primitive in our toolbox.

From my own perspective as the main developer on the main editor for OSM, the reason I don’t like relations very much is because:
- every type of node basically works the same.
- every type of linear way basically works the same.
- every type of polygonal area basically works the same 
- every type of relation is an edge case that requires special code in order not to break.  

Relations are also problematic because they are unbounded.  Want to make a boundary relation with a million child ways?  This is allowed.  Want to ensure that all those ways are connected?  It may take minutes to download them all.  

They’re almost even a security threat.  I’m willing to bet a black hat could design and upload a relation that would destroy OSM.. Or at least, crash every piece of software in the stack that we rely on:  mapnik, osmium, and any editor that tries to touch it.  

Anyway, I’m not totally against them, but every one of them is different and I can't spend weeks or months supporting every kind of relation or public transport schema people dream up unless it’s super critical for building a useful map (like turn restrictions).  They are really best for features that can not be mapped any other way.

Thanks, Bryan

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