Arena football is a variety of eight-man gridiron football. The game is played indoors on a smaller field than American or Canadian football, designed to fit in the same surface area as a standard North American ice hockey rink, resulting in a faster and higher-scoring game that can be played on the floors of indoor arenas. The sport was invented in 1981, and patented in 1987, by Jim Foster, a former executive of the National Football League and the United States Football League. The name is trademarked by Gridiron Enterprises and had a proprietary format until its patent expired in 2007.