[Tagging] Relation for saying "x is attached to y"?

Steve Bennett stevagewp at gmail.com
Mon Aug 30 14:38:04 BST 2010

On Mon, Aug 30, 2010 at 11:18 PM, Richard Welty <rwelty at averillpark.net> wrote:
> i'd lean towards site relations being useful because i think that
> the computational complexity of doing lots of polygon intersections
> is being underestimated. yes, for small bounding boxes it's ok,
> but consider if you needed to do it on a larger scale, it'd make
> certain tasks completely unreasonable (i'm not sure what those
> tasks might be yet, haven't thought about it.)

Yep. Polygon collisions can also be accidental, like when two objects
from slightly different sources (say one gps, one aerial imagery) are
near each other. A relation is a very explicit statement.

Other generic relation types that would be very useful:
- "these objects are mutually accessible by foot" (to avoid having to
invent artificial foot paths in order to get good routing)
- "these objects express the same thing as that object but in more
detail" (eg, one line representing a pair or more of train lines)
- "these objects are one" (like a very generic multipolygon, could
also work to form "multiways")


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