This book begins with theoretical coverage or relational systems, and proceeds through the design stages of a system that can serve both as an example and pattern design. It demonstrates that the development of REQUIEM (RElational Query and Update Interactive SystEM) involves many aspects of information processing and systems programming, and elaborates on the entire source implementation of this prototype system in detail. This book is aimed at advanced students, researchers, and professionals. One of the objectives of the REQUIEM system is to provide a solid foundation for further development and experimentation with new ideas and features, to adapt and improve upon the source code included in this material.