Complex Problems and Systems

In the previous chapters we have considered a single decision plant with one unified form of the uncertainty based on random, uncertain or fuzzy variables. Complex problems arise when there are different forms of uncertainty in the knowledge representation of a single plant or when there are different levels of uncertainty concerning a single plant. If the relational knowledge representation presented in Chapter 2 is considered as a basic level, then the description of unknown parameters in the relations, using random or uncertain variables, forms the second (the upper) level of uncertainty or the second-order uncertainty, as was explained in Sect. 3.6 for the relational and random levels. The first part of this chapter concerns this kind of complex problems.