From DDL Wiki
Bi-Level Integrated System Synthesis (BLISS) is a decomposition technique (Sobieszczanski-Sobieski et al., 2003). BLISS decomposes a design optimization problem into a system optimization and a set of subsystem optimizations that are used to generate approximations of the subsystems. For example, BLISS has been applied to the design of a supersonic business jet (Kim et al., 2004). In this problem, the structures, aerodynamics, propulsion, and performance were the disciplinary subsystems.
Kim, H., Ragon, S., Soremekun, G., and Malone, B., 2004, Flexible Approximation Model for Bi-Level Integrated System Synthesis, AIAA 2004-4545, 10th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, Albany, New York, August 30 - September 1, 2004.
Sobieszczanski-Sobieski, J., Altus, T.D., Phillips, M., and Sandusky, R., 2003, Bi-Level Integrated System Synthesis for Concurrent and Distributed Processing, AIAA Journal, Volume 41, Number 10, pages 1996-2002.