[Tagging] type=bounday

[Minh Nguyen]

Vào lúc 10:04 2022-03-25, David Marchal via Tagging đã viết:
> Multipolygons were considered but boundary was preferred because such 
> areas are often subject to a separate set of laws, akin to a protected 
> area, but less strict, so it was more akin to a boundaried area than to 
> a simple multipolygon.
> 
> That being said, as you said, this changes almost nothing for mapping.

Boundary relations can indicate the capital (admin_centre) or cultural 
center (label) of an administrative area. These roles are very handy for 
edge cases such as a city that developed outwards away from a coast but 
kept its cultural and commercial center on the coast, or the occasional 
U.S. county whose county seat is in a neighboring county. [1] The 
multipolygon type is a purely geometric type, so these roles would've 
been problematic from an interoperability standpoint.

The boundary relation type has since been extended with another 
multipolygon-incompatible role for political subdivisions (subarea). 
Despite misgivings about the subarea role in general, I've been eyeing 
it as a solution to some of Ohio's township boundary edge cases [2], 
because it would be more machine-readable than is_in:*.

[1] https://www.openstreetmap.org/relation/1425399
[2] https://www.openstreetmap.org/user/Minh%20Nguyen/diary/398893

-- 
minh at nguyen.cincinnati.oh.us