Since its inception, the theory of fuzzy sets has advanced in a variety of ways and in many disciplines. Applications of fuzzy technology can be found in artificial intelligence, computer science, control engineering, decision theory, expert systems, logic, management science, operations research, robotics, and others. Theoretical advances have been made in many directions.
The primary goal of Fuzzy Set Theory - and its Applications, Fourth Edition is to provide a textbook for courses in fuzzy set theory, and a book that can be used as an introduction. To balance the character of a textbook with the dynamic nature of this research, many useful references have been added to develop a deeper understanding for the interested reader.
Fuzzy Set Theory - and its Applications, Fourth Edition updates the research agenda with chapters on possibility theory, fuzzy logic and approximate reasoning, expert systems, fuzzy control, fuzzy data analysis, decision making and fuzzy set models in operations research. Chapters have been updated and extended exercises are included.

From the preface to the Fourth Edition by H.-J. Zimmermann
**`I hope that this new edition of my textbook will help to keep respective courses in universities and elsewhere up-to-date and challenging and motivating for students as well as professors. It may also be useful for practitioners that want to update their knowledge of fuzzy technology and look for new applications in their area.'**

Autorentext
Prof. em. Dr. Drs. h. c. Hans-Jürgen Zimmermann war bis 1999 Inhaber des Lehrstuhls für Unternehmensforschung (Operations Research) an der RWTH Aachen und ist Wissenschaftlicher Leiter der ELITE (European Laboratory for Intelligent Techniques Engineering) sowie wissenschaftlicher Beirat des Instituts für Operations Research und Management, Inform GmbH, in Aachen.

Inhalt
1 Introduction to Fuzzy Sets.- 1.1 Crispness, Vagueness, Fuzziness, Uncertainty.- 1.2 Fuzzy Set Theory.- I: Fuzzy Mathematics.- 2 Fuzzy Sets-Basic Definitions.- 3 Extensions.- 4 Fuzzy Measures and Measures of Fuzziness.- 5 The Extension Principle and Applications.- 6 Fuzzy Relations and Fuzzy Graphs.- 7 Fuzzy Analysis.- 8 Uncertainty Modeling.- II: Applications of Fuzzy Set Theory.- 9 Fuzzy Logic and Approximate Reasoning.- 10 Fuzzy Sets and Expert Systems.- 11 Fuzzy Control.- 12 Fuzzy Data Bases and Queries.- 13 Fuzzy Data Analysis.- 14 Decision Making in Fuzzy Environments.- 15 Applications of Fuzzy Sets in Engineering and Management.- 16 Empirical Research in Fuzzy Set Theory.- 17 Future Perspectives.- Abbreviations of Frequently Cited Journals.