Johan van den Akker

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In some key database applications, such as data mining, a sequence of interdependent queries may be posed simultaneously to the DBMS. The optimization of such sequences is called multi-query optimization, and it attempts to exploit these dependencies in the derivation of a query evaluation plan (qep). Although it has been observed and demonstrated by(More)
This report deenes Degas, an advanced active data model that is novel in two ways. The rst innovation is object autonomy, an extreme form of distributed control. In comparison to more traditional approaches, autonomous objects also encapsulate rule deenitions to make them active. The second innovation of Degas is its temporal aspect. Active databases have(More)
Developments in distribution and networking of computing power raise questions about the feasibility of centralised control in an information system. At the same time the move towards information systems ranging over a number of diierent organisations brings us systems where central control is not desired. This asks for systems built of components that can(More)
This report discusses application design for active databases, in particular for the active object-based database programming language Degas. In Degas one modularisation principle, the object, is applied to all elements of the application, including rules. We discuss a design process consisting of four phases, corresponding with the four kinds of(More)
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