geometryAggregates.xsd

See ISO/DIS 19136 12.3.
Geometric aggregates (i.e. instances of a subtype of gml:AbstractGeometricAggregateType) are arbitrary aggregations of geometry elements. They are not assumed to have any additional internal structure and are used to "collect" pieces of geometry of a specified type. Application schemas may use aggregates for features that use multiple geometric objects in their representations.