The role argument is a relation, or the name of a relation.
The value argument is the new value of role. If role is single-valued and value is a list, the list is interpreted as a single role filler. If role is multiple-valued, then value must be a list, and each member of the list is interpreted as a separate filler.
(defrelation r :characteristics :single-valued) (fset-value (fi Joe) (fr r) '(3 4 5)) ==> (3 4 5) (fset-value (fi Joe) (fr r) (fi Sue)) ==> |I|SUE (defrelation rr) (fset-value (fi Joe) 'rr (list (fi Mary) (fi Sue))) ==> (|I|MARY |I|SUE)