def create_stratum_name(stratification_name, stratum_name, joining_string="X"):
    """
    generate a name string to represent a particular stratum within a requested stratification

    :param stratification_name: str
        the "stratification" or rationale for implementing the current stratification process
    :param stratum_name: str
        name of the stratum within the stratification
    :param joining_string: str
        the character to add to the front to indicate that this string is the extension of the existing one
        in SUMMER, capitals are reserved for non-user-requested strings, in this case "X" is used as the default
    :return: str
        the composite string for the stratification
    """
    return joining_string + "%s_%s" % (stratification_name, str(stratum_name))