The Algres testbed of CHIMERA: an active object-oriented database system

Chimera i? a novel database language integrating an object-oriented data model, a declarative query language based on deductive rules, and an active rule language for reactive processing. In most active object-oriented databases, active rules are associated with objects through methods—rules are triggered by method activations, and are used as devices for testing preand post-conditions for method applications to individual object instances. The Chimera approach is substantially different: it uses set-orzented active rules, activated as the effect of several, logically indistinguishable events affecting multiple object instances. This approach is consistent with the rest of Chimera, which supports a set-oriented, declarative query and update language. Object-orientation in Chimera guarantees important advantages over relational active rules, due to the use of object tdenttjiers. In object-oriented databases, object identifiers are uniquely associated with each object instance. In rules of Chimera: object-valued variables (i.e., variables ranging over obJect identifiers) provide a powerful bzndtng passing mechanism for linking events to conditions and conditions to actions, thus bridging the three syntactic components of active rules. Active rules in Chimera have several innovative features: