Smart Key - RDB Mode

If pressed within an rdb-mode buffer which manipulates in-memory,
relational databases (part of InfoDock):
  ACTION KEY
    (1) on the name of a relation, the relation’s full table is shown;
    (2) on an attribute name, all attribute columns aside from this one
        are removed from the relation display;
    (3) to the left of a tuple (row), the tuple is removed from the display;
    (4) on an attribute value, all tuples (rows) which do not contain
        the selected attribute value are removed from the current table display;
    (5) on or after the last line in the buffer, the current database is redisplayed;
    (6) anywhere else (except the end of a line), the last command is undone."

  ASSIST KEY
    (1) on the name of a relation, the relation is removed from the display;
    (2) on an attribute name, the attribute column is removed from the relation
        display;
    (3) to the left of a tuple (row), the tuple is removed from the display;
    (4) on an attribute value, all tuples with the same attribute value are
        removed from the display."