Summary form only given. FLORID-F-LOgic Reasoning In Databases-is a deductive object oriented database system incorporating F-logic (M. Kifer et al., 1995) as a data definition and query language and combining the advantages of deductive databases with the rich modelling capabilities of object oriented concepts. F-logic provides complex objects, uniform handling of data and metadata, rule defined class hierarchy and signatures, nonmonotonic multiple inheritance, equating of objects by rules and variables ranging over methods and classes. Moreover, FLORID extends F-logic by path expressions (J. Frohn et al., 1994) to facilitate object navigation. Because of its powerful properties, F-logic cannot be mapped onto a relational data model by transforming classes into relations. Hence, it was a major design goal to use an object oriented data representation in FLORID. All information about one object is stored in an object frame which has a unique OID. Several (external) object names may refer to the same OID, thus defining an equivalence relation between objects. Frames consist of slots for method applications or class membership, enabling schema modifications during the evaluation by deriving new signatures, subclass relationships or class memberships. The collection of all frames forms an object world.