The hype is over - and this is fine!Advanced Planning Systems (APS) have become a mature technologyin the past years. Investments in APS have to undergo the same standardsoftware evaluation and financial appraisal process as any other investment. Itno longer suffices to argue that“we have to be at the front edge of technology”.And still there is a large number of rewarding applications for APS. Threeof these have become new case studies in this fourth edition. Unfortunately,a fourth case study has been withdrawn in the last minute because the clientcompany regards its APS solution a key element of becoming the leader inits sector - expertise which they do not want to share with their competitors.A second development to mention is the tendency to avoid the term“System”in AP”S”. Instead some prefer the term Advanced Planning Moduleswhich better reflects the capability to combine some of its modules withother software components (e.g. for Supply Chain Event Management) toform an individual Supply Chain (SC) solution. However, the informationflows among modules described in this book now even become more importantfor the quality of the SC solution generated. Hence, there is no reasonfor us to refrain from the term APS or to change the concept of our book.Readers familiar with the third edition will realize that not only chaptershave been reorganized and updated to the state-of-the-art but also thatthere has been much fine-tuning of technical issues like for the index andthe references. This is due to Christian Seipl who took over the “burden” ofadministering the chapters. Many thanks to him! We are also indebted to anumber of consultants and practitioners for providing advice and proofreadingparts of the book, especially with respect to the description of selectedAPS.Now it is up to you, dear reader, to make the best use of this fourthedition!