“…Assumptions are widely used in preliminary design tasks. In traditional computational models, such as those using assumption-based truth maintenance architectures [ATMS (De Kleer, 1986)], an assumption is mainly considered to be a defeasible decision useful to initiate the search process and guide it through incomplete knowledge (Logan et al, 1992;Sham, 1993). Such use of assump-Reprint requests to: Djamila Haroud, Artificial Intelligence Laboratory (LIA), Swiss Federal Institute of Technology (EPFL), IN-Ecublens, 1015 Lausanne, Switzerland.…”