This text presents a specialized topic in the area of database management. Every researcher working in this area may use some of the techniques presented here. The complexity of the subject is handled in a detailed way so as to give down-to-earth explanations. One of the unique features of the work is the presentation of a collective view of common issues prevailing in several domains, including distributed databases. This approach enables the reader to appreciate the use of the tools and techniques developed, in the context of distributed databases applied to several domains, thus favoring multi-disciplinary research activity.