Rael Isacowitz is the founder of BASI Pilates and one of Pilates' best-known instructors. System 17 is the intermediate part of a 3 part DVD series - System 7, 17 and 27 for beginner through advanced students.
More on Rael Isacowitz and BASI Pilates at About.com:
DVD Review: Rael Pilates System 17
Book Review: Pilates, by Rael Isacowitz
Interview with Rael Isacowitz: Pilates - Art, Science and Passion
BASI Pilates Teacher Training Show and Tell