Integrity constraints represent an important source of information about the real world. They are usually used to define constraints on data (functional dependencies, inclusion dependencies, etc.). Nowadays integrity constraints have a wide applicability in several contexts such as semantic query optimization, cooperative query answering, database integration and view update. Often databases may be inconsistent with respect to integrity constraints, that is, one or more integrity constraints are not satisfied. This may happen, for instance, when the database is obtained from the integration of different information sources. The integration of knowledge from multiple sources is an important aspect in several areas such as data warehousing, database integration, automated reasoning systems and active reactive databases.