In each case, the SELECT subquery inside the CAST/MULTISET expression selects the
data we require (in the first case, a list of next of kin for the member of staff and in the
second case, a list of telephone numbers for the branch). The MULTISET keyword indicates
that this is a list rather than a singleton value, and the CAST operator then casts this
list to the required type. Note also the use of the MAKE_REF operator, which creates a
REF to a row of an object view or a row in an object table whose object identifier is
primary-key based.