def make_identifier(classname):
    """
    Given a class name (e.g. CountryData) return an identifer
    for the data-table for that class.
    """
    identifier = [ classname[0].lower() ]
    for c in classname[1:]:
        if c.isupper():
            identifier.extend(["_", c.lower()])
        else:
            identifier.append(c)
            
    return "".join(identifier)