[Tagging] My "weirdly unnatural aversion to relations"
joseph.eisenberg at gmail.com
Sun Sep 30 03:26:43 UTC 2018
Would it be helpful if there were several simpler database primitives for
several of the simplest types of relations?
I know people have already talked for years about adding a true area object
(which now we imitate with closed ways)
Could we also have a linear feature made up of ways only? This would
include the current route and waterway relations. Would something like this
be helpful, especially if there were a limit to how many ways could be
Could multipolygons be specifically defined, perhaps as a type of area?
I do think it is strange that any random collection of nodes and ways can
form a relation. And the ability to make relations out of other relations
is also confusing.
But it would be quite helpful to be able to make relations from smaller
relations, in the simpler cases of a Lake with an island inside
(multipolygon in a multipolygon), or a long highway made of shorter routes,
or a long river made of shorter waterway relations.
On Sun, Sep 30, 2018 at 12:01 PM Bryan Housel <bhousel at gmail.com> wrote:
> 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
> Tagging mailing list
> Tagging at openstreetmap.org
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