This paper proposes the unification of active and passive objects in object-oriented operating systems. With such a unification, programmers can concentrate on programming an algorithm without having to consider how objects are used and executed. Also, all objects can be migrated in a distributed system. To achieve this unification, meta level scheduling control is introduced, and the scheduling policy is determined at object creation time. We named this system Cognac. In Cognac, the execution domain of an object is an object cluster, in which some metaobjects control the execution of member objects at run-time. The scheduler metaobject manages method invocation and the status of its member objects. Since all objects' attributes are managed by metaobjects, mutual exclusion is guaranteed.
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