Based on the above reasoning, the editors identified key researchers and practitioners in each of the aforementioned categories and invited them to contribute a corresponding work to this book. However, as the authors’ contributions started to arrive, the editors also started to realize that although these categories participate in each chapter to different degrees, none of them can ever be totally obsolete from them. Moreover, it seems that theory and methods are inherent in the development of tools and applications and inversely the application is also inherent in the motivation and presentation of tools and methods.