  Possibility theory offers either a qualitive, or a numerical framework for
representing uncertainty, in terms of dual measures of possibility and
necessity. This leads to the existence of two kinds of possibilistic causal
graphs where the conditioning is either based on the minimum, or the product
operator. Benferhat et al. (1999) have investigated the connections between
min-based graphs and possibilistic logic bases (made of classical formulas
weighted in terms of certainty). This paper deals with a more difficult issue :
the product-based graphical representations of possibilistic bases, which
provides an easy structural reading of possibilistic bases. Moreover, this
paper also provides another reading of possibilistic bases in terms of
comparative preferences of the form "in the context p, q is preferred to not
q". This enables us to explicit preferences underlying a set of goals with
different levels of priority.
