base function for extracting a simple parameter value.
    :param tree: the parameters tree.
    :param kind: the xml-tag name of the parameter.
    :param name: the name of the parameter.
    :returns value: the content of the parameter 'Value' as string.

def _simple_string_value(tree, kind, name):
    """ base function for extracting a simple parameter value.
    :param tree: the parameters tree.
    :param kind: the xml-tag name of the parameter.
    :param name: the name of the parameter.
    :returns value: the content of the parameter 'Value' as string."""
    query = ".//{kind}[@Name='{name}']/Value".format(kind=kind, name=name)
    return tree.find(query).text