In recent years, many researchers have presented different forecasting methods to deal with forecasting problems based on fuzzy time series. When we deal with forecasting problems using fuzzy time series, it is important to decide the length of each interval in the universe of discourse due to the fact that it will affect the forecasting accuracy rate. In this article, we present a new method to deal with the forecasting problems based on high-order fuzzy time series and genetic algorithms, where the length of each interval in the universe of discourse is tuned by using genetic algorithms, and the historical enrollments of the University of Alabama are used to illustrate the forecasting process of the proposed method. The proposed method can achieve a higher forecasting accuracy rate than the existing methods. © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 485–501, 2006.

A fuzzy Petri net model (FPN) is presented to represent the fuzzy production rule of a rule-based system in which a fuzzy production rule describes the fuzzy relation between two propositions. Based on the fuzzy Petri net model, an efficient algorithm is proposed to perform fuzzy reasoning automatically. It can determine whether an antecedent-consequence relationship exists from proposition d/sub s/ to proposition d/sub j/, where d/sub s/ not=d/sub j/. If the degree of truth of proposition d/sub s/ is given, then the degrees of truth of proposition d/sub j/ can be evaluated. The formal description of the model and the fuzzy reasoning algorithm are shown in detail. The upper bound of the time complexity of the fuzzy reasoning algorithm is O(nm), where n is the number of places and m is the number of transitions. Its execution time is proportional to the number of nodes in a sprouting tree generated by the algorithm only generates necessary reasoning paths from a starting place to a goal place, it can be executed very efficiently.>