This line of investigation was originally inspired by the comments of Dr. J. Ousterhout regarding relationships between files. We are grateful to Prof. M. Baker for her support in working with the Sprite file system traces, B. Sherrod for his insightful comments and continued support, R. Appleton for sharing advance copies of his work and his experiences, T. Van Vleck for his many comments and his idea of a parameterless selection technique, Dr. L. F. Cabrera for his input and guidance, and to the many other people who offered their time and comments.