This volume aims to present recent advances in database technology from the viewpoint of the novel database paradigms proposed in the last decade. It focuses on the theory of the extended relational model, and an example of an extended relational database programming language, Algres, is described. A free copy of Algres complements this work, and is available on the Internet. The work should be of interest to graduate studen ts following advanced database courses, advanced data-oriented applications developers, and researchers in the field of database programming languages and software engineering who need a flexible prototyping platform for the development of software tools.