From the Introduction chapter in the Story Engine Universal Rules (Revised Edition) book:
Story Engine came into existence in 1996 as the rules system for Maelstrom Storytelling. It was redesigned for universal play in 1999. One of the first games to truly handle roleplaying as a story game, it was the first set of rules that was "scene based" - an idea that has become more and more popular as story games escape the confines of "round based" rules. Story Engine also further evovled the mechanics of "adjective based" characters, an idea that had appeared in games like Theatrix (Backstage Press 1993) and Over the Edge (Atlas Games 1992) as well as various diceless systems.