1.0 2 information structures, and the runtime efficiency available using lower level data structures. We believe these runtime inefficiencies can be remedied by providing a library of representations for the information structures and a user assisted automatic system to choose appropriate elements from this library for the user's programs. The main problems in such an automatic approach are: 1). Building a library of representations; 2). Characterizing the properties of these representations; 3). understanding how the user's program actually uses the abstract information structures; and -4)....