[Tagging] Boundary Relations. What's a subarea used for?

[Dave F.]

Hi

This UK county boundary (admin level = 6):
http://www.openstreetmap.org/relation/57533#map=9/51.1854/-1.8237

contains nested boundary relations (tagged with role=subarea) with 
numerically higher admin levels:
http://www.openstreetmap.org/relation/3410643#map=13/51.3398/-2.2428

Are they relevant? If so, what are they for? The wiki suggests they're 
superseded:
http://wiki.openstreetmap.org/wiki/Relation:boundary#Relation_members

To me, subarea appears to be used in a similar way to the superseded 
'is_in' tag, For the same reasons that tag was deprecated, mathematics & 
the admin_level tag can be used to determine if one polygon is inside 
another. They seem to be purely extra baggage

Am I missing something or can these nested relations be removed?

Cheers
Dave F.





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