The ATTACH TO COMPOSITE command attaches a controlled element to
    the composite you specify. The element then becomes a child of
    the composite to which you are attaching.

    Before you issue the ATTACH TO COMPOSITE command, you must have
    set a context and reserved a composite. The SHOW CONTEXT and SHOW
    RESERVATIONS commands indicate whether these conditions exist.

    You can use the ATTACH TO COMPOSITE command in conjunction
    with the DEFINE, RESERVE, REPLACE, and DETACH commands to link
    collections in collection hierarchies. See the DEFINE COLLECTION
    command for an example of a collection hierarchy.

    You can also use the DETACH FROM COMPOSITE and ATTACH TO
    COMPOSITE commands to move between lines of descent. See the
    Oracle CDD/Repository Architecture Manual for more information on
    lines of descent.