Bug 127861 [DataBinding] Mark API provisional
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/databinding/updatables/UnionSet.java
IReadableSet readableSet = children[i];
			
			if (readableSet.isStale()) {
				return true;
			}
		}
    	return false;
    }
	
	/**
	 * Adds a new set to this union
	 * 
	 * @param s set to add to the union
	 */
	public void add(IReadableSet s) {
		Assert.isTrue(!isDisposed());
		Assert.isNotNull(s);
		
		childSets.add(s);
		
		
		if (refCounts != null) {
			initChild(s);
		}
	}
	
	/**
	 * Removes a set from this union
	 * 
	 * @param s set to remove from the union