/// <summary>
        /// Compares openDL and closedDL.  Returns true if they have the same bases and value.
        /// </summary>
        /// <param name="openDL"></param>
        /// <param name="closedDL"></param>
        /// <returns></returns>
        public static bool IsValidOpenClosedPair(IWitness openDL, IStatement closedDL)
        {
            if ((openDL == null) ||
                (closedDL == null))
            {
                return(false);
            }
            if ((!openDL.IsWitness) || (closedDL.IsWitness))
            {
                return(false);
            }

            IStatement expectedClosedDL = openDL.GetStatement();

            return(expectedClosedDL.Equals(closedDL));
        }