Which category won the Sundance Film Festival award in 1998?
CREATE TABLE "awards_and_nominations" (
  "year" real,
  "award" text,
  "category" text,
  "film_or_series" text,
  "result" text
);
SELECT "category" FROM "awards_and_nominations" WHERE "result"='won' AND "year"=1998 AND "award"='sundance film festival';