/// <summary>
        /// Returns a string representation of the formula
        /// </summary>
        public override string FormulaRepresentation()
        {
            string strOperationType = GetWFSOperationTypeString();
            string strLeftOperand   = LeftOperand.FormulaRepresentation();
            string strRightOperand  = RightOperand.FormulaRepresentation();
            string str = "(" + strLeftOperand + " " + strOperationType + " " + strRightOperand + ")";

            return(str);
        }