This work contains seven contributions on the rapidly evolving research area of constraints and databases. It is a collection of research articles that have been compiled as a tribute to Paris C. Kanellakis, one of the pioneers in the field. Constraints have long been used for maintaining the integrity of databases. More recently, constraint databases have emerged where databases store and manipulate data in the form of constraints. The generality of constraint databases makes them highly attractive for many applications. Constraints provide a uniform mechanism for describing heterogenous data, and advanced constraint solving methods can be used for efficient manipulation of constraint data. The articles included in this book cover the range of topics involving constraints and databases; join algorithms, evaluation methods, applications (for example, data mining) and implementations of constraint databases, as well as more traditional topics such as integrity constraint maintenance.