To avoid accidentally deleting or updating all rows in a table CQL raises an exception if there is no WHERE restriction.
Sometimes however you really do need to delete or update all rows in a table.
To support this requirement in a disciplined way (and to avoid the creation of "dummy" WHERE restrictions) the keyword absence_of_where_restriction_is_deliberate has been added. For example:
{[],
update(se_lt_x, [c-10]),
@ :: [],
absence_of_where_restriction_is_deliberate}