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For each class, the table defines any other classes which are subordinate to it. Only classes that support containment and scoping should have an SDT. See also ``Subordinates definition table (SDT)''.
This example defines two subordinate classes of the class ``sco user''. These two subordinate classes (``sco workProjects'' and ``sco vacations'') will each have a list operation which, when called with an object instance of the ``sco user'' class, will list which object instances of the ``sco user'' class it is contained by.
Example SDT (Tcl)
set users(subordinates) {
        {sco workProjects}
        {sco vacations}
}
Example SDT (C/C++)
static objectClass_pt subordinates[] = {
        "sco workProjects",
        "sco vacations",
        NULL
};