Preserving and generating objects in the LIVING IN A LATTICE rule language

LIVING IN A LATTICE is presented as a rule-based query language for an object-oriented database model. The model supports complex objects, object identity, and is-a-relationships. The instances are described by object relations, which are functions from a set of objects to value sets and other object sets. The rule language is based on object-terms which provide an access to objects via is-a-relationships. Rules are divided into two classes: object-preserving rules manipulating existing objects and object-generating ones creating objects with properties derived from existing objects. The derived object sets are included in a lattice of object types. Some conditions are given under which the instances of the rule´s heads are consistent, i.e., where the properties of the derived objects are functionally determined by the objects