Active Relationships: A Means for Controlled Propagation of Information and Activities in Databases
In many complex applications (design, manufacturing, workflow management, etc.) information about activities on specific objects affect related objects and result in subsequent activities on distant objects. The way in which objects are influenced by actions on related objects is dependent on the operational semantics of the relationship. To capture this semantics, we introduce the concept of "active relationships" which contain a description of the activity propagation as an integral part of the relationship type definition. Active relationships allow to separate the specification of local activities and their global consequences and to solve typical problems concerning consistency control, configuration management, resource activation, etc. The paper discusses the features of active relationships and their integration into an object-oriented environment by means of several application examples. In addition, it describes an implementation of active relationships based on an object-oriented database and the use of this implementation for coupling two subsystems to an integrated system.
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