More "complex" modeling schemas can represent an object as a composition of "simple sub-objects". Examples: represent in an astronomical map a star by a "point" and a binary star by "two points"; represent in geographical map a river with a "line", for its source stream, and with an strip-"area", for the rest of the river. These schemas can use the above classes, uniform composition classes ("multi-point", "multi-line" and "multi-area") and heterogeneous composition ("points"+"lines" as "object of dimension 1", "points"+"lines"+"areas" as "object of dimension 2").