This paper presents an approach for diagnosis and maintenance of compl
ex naval systems that incorporates both rule-based and probability-bas
ed reasoning. This type of diagnosis is useful in situations where exp
eriential knowledge and procedures coexist with statistical reliabilit
y data about the system. Effectively using the two types of knowledge
is typically difficult, but in this study a blackboard-like control ar
chitecture is used to successfully interface these two knowledge compo
nents into an integrated diagnostic model. A case study of diagnostic
maintenance of a shipboard weapon system is presented.