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Object

-              v80
+              v81
 A water object ({{{natural=water}}}), a building ({{{building=*}}}) or administrative boundary ({{{admin_level=*}}} tag) usually consist of the  multiple spatially separated parts belonging to the one object. More importantly, each of these parts can have exclusions ([https://en.wikipedia.org/wiki/Enclave_and_exclave enclaves/exclave] or simply islands or swamps in the water basins).
+* Parts are created using "{{{outer}}}" role
+* Holes inside parts - using "{{{inner}}}" role
+* Parts are created using "{{{outer}}}" role. ''Each multi-polygon should have at least one outer part''.
+* Holes inside parts - using "{{{inner}}}" role. ''Each part can have from 0 to N holes''.
 * Ways that form a ring where all ways are connected between each other using common nodes (JOSM will warn you about mistakes during validation)
 * rarely, if nesting is more complex than ''single outer'' and ''single inner ring'', role swapping can continue: outer-inner-outer-inner-...
+* Rarely, holes can be nested. If nesting is more complex than ''single outer'' and ''single inner ring'', role swapping can continue: outer-inner-outer-inner-...
 * Outer and inner rings shouldn't have common nodes (but validator will warn you about this and other mistakes)