From Qualitative to Quantitative Probabilistic Networks

Quantification is well known to be a major ob­ stacle in the construction of a probabilistic net­ work, especially when relying on human experts for this purpose. The construction of a qualitative probabilistic network has been proposed as an initial step in a network's quantification, since the qualitative network can be used to gain prelimi­ nary insight in the projected network's reasoning behaviour. We extend on this idea and present a new type of network in which both signs and numbers are specified; we further present an associated algorithm for probabilistic inference. Building upon these semi-qualitative networks, a probabilistic network can be quantified and stud­ ied in a stepwise manner. As a result, modelling inadequacies can be detected and amended at an early stage in the quantification process.