[OSM-dev] Topology requirements for shorelines

[Ben Supnik]

Hi Y'all,

It appears that for the most part OSM data is relatively unstructured 
(compared to vector data sets that, for example, contain full topology).

But...what about water bodies?  In particular, if a land mass is not 
exactly wrapped once by a counter-clockwise winding of "ways", does the 
tile renderer have trouble correctly filling in land and water?

- What happens if there are overlapped coastline ways?
- What happens if there are holes in the coatlines?
- What happens if there are double windings (imagine two full counter 
clockwise revolutions making interlocked loops).

I am trying to understand what "mistakes" in coastlines would affect the 
slippy map (and thus be obvious to everyone) vs. data issues that might 
only be useful to machine processing algorithms.

Thanks!
Ben

PS sorry for 10,000 questions...there's a ton to get up to speed on here!
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