The paper presents a causal-probabilistic approach to the technical di
agnosis in which the solution of the technical diagnostic problem is c
onsidered as a probabilistic inference on a special kind of Bayesian n
etworks called Diagnostic Bayesian Networks. A mechanism of probabilis
tic inference and an algorithm for inference control are described. It
is proved that a diagnostic problem represented by a singly connected
Diagnostic Bayesian network can be decomposed to a sequence of subpro
blems with directed tree or multitree topology which are exactly solve
d in the sense of minimizing the average number of executed tests. The
applications of the approach and future trends are briefly discussed.