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Abstract : |
This paper describes the design and implementation of NAOS, an active rule component in the objectoriented database system O 2. The contribution of this work is related to two main aspects. The first concerns the integration of the rule concept within the O 2 model, providing a way to structure applications. Rules are part of a schema and do not belong to a class. Program execution and data manipulation, including method calls, can be driven on rules. The second aspect concerns the way NAOS interacts with O 2 Engine, the kernel of the O 2 system. To support a reactive capability the object manager semantics has been extended, thus providing an efficient event detection. Applications produce events and the subscribed event types react to these events. As a result, rules are triggered. The semantics of rule processing we provide is achieved through functions associated with event types during their subscription. The subscription mechanism is general enough to be used by any event driven applications. 1, |
