  The domain of spare parts forecasting is examined, and is found to present
unique uncertainty based problems in the architectural design of a
knowledge-based system. A mixture of different uncertainty paradigms is
required for the solution, with an intriguing combinatoric problem arising from
an uncertain choice of inference engines. Thus, uncertainty in the system is
manifested in two different meta-levels. The different uncertainty paradigms
and meta-levels must be integrated into a functioning whole. FRED is an example
of a difficult real-world domain to which no existing uncertainty approach is
completely appropriate. This paper discusses the architecture of FRED,
highlighting: the points of uncertainty and other interesting features of the
domain, the specific implications of those features on the system design
(including the combinatoric explosions), their current implementation & future
plans,and other problems and issues with the architecture.
