Deductive Databases are coming of age with the emergence of efficient and easy to use systems that support queries, reasoning, and application development on databases through declarative logic-based languages. Building on solid theoretical foundations, the field has benefited in the recent years form dramatic advances in the enabling technology. This progress is demonstrated by the completion of prototype systems offering such levels of generality, performance and robustness that they support well complex application development. Valuable know-how has emerged from the experience of building and using these systems: we have learned about algorithms and architectures for building powerful deductive database systems, and we begin to understand the programming environments and paradigms they are conducive to. Thus, several application areas have been identified where these systems are particularly effective, including areas well beyond the domain of traditional database applications. Fin...