Typically, when building an aggregator, one wants to be able to
specify how the Preferences on the MPTask of a Container will
depend on the Preferences of its parent Task(s). This interface
encapsulates that behavior.
The return value of this method should be an Enumeration ofPreferences, suitable to be the input value of the NewTask interface'ssetPreferences method. See Also:org.cougaar.planning.ldm.plan.NewTask.setPreferences