The problem of verifying the integrity of fuzzy knowledge bases is discussed. An approach to find potential inconsistencies in fuzzy rule based systems is described. The approach models the knowledge base as a High Level Fuzzy Petri Net and uses the structural properties of the net for verification. Basic notions on approximate reasoning, regular and hierarchical High Level Fuzzy Petri Nets are also given. The method used for consistency checking is reviewed through the analysis of several cases including simple and chaining rules. Procedures for discovering potential inconsistencies at both local and global levels are described. © 1994.642175193Agarwal, Tanniru, A Petri-Net based approach for verifying the integrity of production systems (1992) Int. J. Man-Machine Studies, 36, pp. 447-468Chang, Hall, The validation of fuzzy knowledge-based systems (1992) Fuzzy Logic and the Management of Uncertainty, pp. 589-604. , L. Zadeh, J. Kacprzyk, John Wiley & Sons, New YorkChen, Ke, Chang, Knowledge representation using fuzzy Petri nets (1990) IEEE Trans. Knowledge and Data Engineering, 2, pp. 311-319Dubois, Prade, Fuzzy sets in approximate reasoning, part 1: inference with possibility distributions (1991) Fuzzy Sets and Systems, 40, pp. 143-202Genrich, Predicate/Transition nets (1986) Petri Nets: Central Models and their Properties, 254, pp. 207-247. , W. Brauer, W. Reisig, G. Rozenberg, 2nd edition, Lecture Notes in Computer Science, Springer-Verlag, BerlinGiordana, Saitta, Modeling production rules by means of predicate transition networks (1985) Information Sciences, 35, pp. 1-41Gupta, Qi, Theory of T-norms and fuzzy inference methods (1991) Fuzzy Sets and Systems, 40, pp. 431-450Leung, So, Inconsistency in fuzzy rule-based expert systems (1990) Proceedings of the International Conference on Fuzzy Logic & Neural Networks, pp. 849-852. , JapanMizumoto, Zimmermann, Comparison of fuzzy reasoning methods (1982) Fuzzy Sets and Systems, 8, pp. 253-283Murata, Petri nets: properties, analysis and applications (1989) Proceedings IEEE, 77, pp. 541-580. , 2nd editionNazareth, Issues in the verification of knowledge in rule-based systems (1989) Int. J. Man-Machine Studies, 30, pp. 255-271Pedrycz, (1989) Fuzzy Control and Fuzzy Systems, , Wiley, New YorkScarpelli, Gomide, Modeling fuzzy reasoning using fuzzy Petri nets (1992) Tech. Rep. RT-DCA 020/92, , 2nd edition, DCA/FEE/UNICAMP, Campinas, SPScarpelli, Gomide, Pedrycz, Modeling fuzzy reasoning using high level fuzzy Petri nets (1992) Tech. Rep. RT-DCA 023/92, , 2nd edition, DCA/FEE/UNICAMP, Campinas, SP, (submitted)Scarpelli, Gomide, Yager, A backward reasoning algorithm for high level fuzzy Petri nets (1993) Tech. Rep. RT-DCA 004/93, , 2nd edition, DCA/FEE/UNICAMP, Campinas, SP, (submitted)Scarpelli, Gomide, Fuzzy reasoning and fuzzy Petri nets (1993) Proc. Fifth IFSA World Congress, pp. 1326-1329. , Seoul, KoreaScarpelli, Gomide, Fuzzy reasoning and fuzzy Petri nets in manufacturing systems modeling (1993) Journal of Intelligent and Fuzzy Systems, 1, pp. 225-241Scarpelli, Gomide, Discovering potential inconsistencies in fuzzy knowledge bases using high level nets (1993) Tech. Rep. RT-DCA 006/93, , 2nd edition, DCA/FEE/UNICAMP, Campinas, SPScarpelli, Modeling, design and verification of fuzzy rule bases using net theory (1993) Doctoral Thesis, , 2nd edition, DCA/FEE/UNICAMP, Campinas, SP, (in Portuguese)Scarpelli, Gomide, Fuzzy reasoning and high level fuzzy Petri nets (1993) Proc. First European Congress on Fuzzy and Intelligent Technologies, , Aachen, GermanyYager, Larsen, On discovering potential inconsistencies in validating uncertain knowledge bases by reflecting on the input (1991) IEEE Trans. on Systems, Man and Cybernetics, 21, pp. 790-801Yager, Connectives and quantifiers in fuzzy sets (1991) Fuzzy Sets and Systems, 40, pp. 39-75Zadeh, Fuzzy sets as a basis for a theory of possibility (1978) Fuzzy Sets and Systems, 1, pp. 3-20Zadeh, A theory of approximate reasoning (1979) Machine Inteligence, 9, pp. 149-194. , 2nd edition, Hayes, Michie, Kulich, John Wiley & Sons, New York