class PartialOrderedSet extends HashSet<E> {

	public boolean allowsABeforeB(final E a, final E b) {
		Set<E> transitiveClosure = this.getTransitiveClosure(b);
		return !transitiveClosure.contains(a);
	}

	public  PartialOrderedSet(final PartialOrderedSet<E> original);
	public  PartialOrderedSet();

}