Albert Benveniste, Ramine Nikoukhah, Alan S. Willsky.Caption title. "November 22, 1991."Includes bibliographical references (p. 25-27).First and second authors supported in part by INRIA-NSF agreement. Third author supported in part by the Air Force Office of Scientific Research. AFOSR-92-5-0002 Third author supported by the National Science Foundation. MIP-9015281 INT-9002393 Third author supported by the Office of Naval Research. N00014-91-J-1004