Dave McNary Film ReporterThe Writers Guild of America West is demanding that the Academy of Motion Picture Arts and Sciences expand its new best picture rules to include mandates against age discrimination.In an open letter posted on the WGA West site, the guild’s Career Longevity Committee urged the Academy to revise the new rules, which were issued Sept. 8 to encourage equitable representation on and off screen in order to better reflect the diversity of the movie-going audience.