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x surrounded_by y if and only if (1) x is adjacent to y and for every region r that is adjacent to x, r overlaps y (2) the shared boundary between x and y occupies the majority of the outermost boundary of x

http://purl.obolibrary.org/obo/IAO_0000125

http://purl.obolibrary.org/obo/RO_0001901

Chris Mungall