X outer_layer_of Y iff: . X :continuant that bearer_of some PATO:laminar . X part_of Y . exists Z :surface . X has_boundary Z . Z boundary_of Y has_boundary: http://purl.obolibrary.org/obo/RO_0002002 boundary_of: http://purl.obolibrary.org/obo/RO_0002000