ASK-INSTANCE-VALUES
===================

syntax: (ask-instance-values 
                        <evaluates-to relation-name>
                        <evaluates-to instance-spec>
                        [:read-dependents 
                            {T | NIL | Var}]
                        [:if-undetermined 

This function returns the value set of the instance 
relation. If ':if-undetermined' is not set to NIL, 
then a 'if-undetermined-action' will be started 
before the relation value is found. If ':read-
dependents' is not set to NIL, then the read-
dependents will be informed after the relation value 
is found.

example: >(ask-instance-values 'place louvre)
         #<set-of CITY (...)>