Schema validation is becoming one of the most important problems in database engineering. By validation we mean the process of checking whether a database schema correctly and adequately describes the users' intended needs and requirements. In this paper we present and discuss six different methods handling schema validation in the deductive database field. All these methods define and check some desirable/undesirable properties that a database schema should/should not satisfy: schema satisfiability, liveliness of a predicate, satisfy: schema satisfiability, liveliness of a predicate, reachability of a formula and redundancy of integrity constraint specifications.