The LOGIDATA+ Language and Semantics

A language for the LOGIDATA+ model is presented. The language is rule-based and allows for the management of complex structures, classes, hierarchies and data functions. Negation is allowed in the body of rules. The semantics is based on a fixpoint operator and represents an extension of ordinary declarative-language semantics. The main issue is the management of oid-invention, that is, the creation and manipulation of objects belonging to the classes of a scheme. In order to correctly deal with negation and multivalued data functions, an extended notion of stratification is introduced.