*/
    public boolean isEmpty () {
        return this.sub_authority_count == 0;
    }


    /**
     * 
     * @return whether the SID is blank (all sub-authorities zero)
     */
    public boolean isBlank () {
        boolean blank = true;
        for ( int sub : this.sub_authority )
            blank = blank && ( sub == 0 );
        return blank;
    }


    /**