@Override
	public int compareTo(LinkTriple other) {
		int diff1 = 0, diff2 = 0, diff3 = 0;
		if ( subj != other.subj ) {
			if ( subj != null )
				diff1 = subj.compareTo(other.subj);		
			else 
				diff1 = 1;
		}
		if ( pred != other.pred ) {
			if ( pred != null )
				diff2 = pred.compareTo(other.pred);					
			else
				diff2 = 1;
		}
		if ( obj != other.obj ) {
			if ( obj != null )
				diff3 = obj.compareTo(other.obj);			
			else
				diff3 = 1;
		}
		if ( diff1 != 0 ) 
			return diff1;
		if ( diff2 != 0 ) 
			return diff2;
		if ( diff3 != 0 ) 
			return diff3;
		return 0;		
	}