Abstract
Objects are collected into an object base because of a presumed need for cooperation among them. In classical object bases the cooperation is based on synchronous, preplanned message exchange. Many of the modern application scenarios such as industrial and office automation with their high volume of concurrent, interleaved, and iterative actions defy preplanning and require the support of a highly dynamic relationships among the objects.
It is the central hypothesis of this paper that the dynamics within such an object base is best covered by the metaphor of communications protocol taken from the telecommunications world. Active objects with their individual threads-of-control establish temporary communication links via a medium which we refer to as activities. Active objects and activity cooperate via a protocol. The main benefit of such an approach is a clear separation of object-local and cooperative aspects of a common task.
The paper augments an existing strongly-typed object-oriented language by active objects with an underlying event processing model based on incoming messages, and by activities with an event processing model based on interfering messages. The interplay between them is demonstrated by an implementation of the classical Two-Phase-Commit protocol as a generic example for negotiations among objects.
This work was partly supported by the German Research Council (Deutsche Forschungsgemeinschaft DFG) under grant SFB346 Project Al.
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© 1994 British Computer Society
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Lockemann, P.C., Walter, HD. (1994). Activities in Object Bases. In: Paton, N.W., Williams, M.H. (eds) Rules in Database Systems. Workshops in Computing. Springer, London. https://doi.org/10.1007/978-1-4471-3225-7_1
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DOI: https://doi.org/10.1007/978-1-4471-3225-7_1
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