Static analysis of ECA rules and use of these rules for incremental computation of general aggregate expressions | Posted on:1997-05-27 | Degree:Ph.D | Type:Dissertation | University:University of Florida | Candidate:Kim, Seung-Kyum | Full Text:PDF | GTID:1468390014482355 | Subject:Computer Science | Abstract/Summary: | | In this work we address two major issues that are related within the framework of active databases. Firstly, we propose a practical approach to rule analysis. We show how alternative rule designer choices can be supported using our approach to achieve confluent rule execution in active databases. Our model employs priority information to resolve conflicts between rules, and uses a rule scheduler based on the topological sort to achieve correct confluent rule executions. Given a rule set, a trigger graph and a dependency graph are built from the information obtained by analyzing the rule set at compile time. The two graphs are combined to form a priority graph, on which the user is requested to specify priorities (or resolve conflicts) only if there exist dependencies in the dependency graph. The user can have multiple priority graphs by specifying different priorities depending on application semantics. From a priority graph, an execution graph is derived for every user transaction that triggers one or more rules. The rule scheduler uses the execution graph. Our model also correctly handles the situation where trigger paths of rules triggered by a user transaction are overlapping, which are not handled by existing models. We prove that our model achieves maximum parallelism in rule executions.; Next, we propose a cache mechanism, called aggregate cache for efficiently supporting complex aggregate computations in data warehouses. We discuss several cache update strategies in the context of maintaining consistency between base databases and aggregates cached in the data warehouse. We formally define the incremental update of aggregates, which is a prime issue for the aggregate cache. Further we classify algebraic aggregates into summative aggregates that include a vast variety of aggregates applicable in data warehouses to support decision making and statistical data analysis. We prove that there is a precise subclass of summative aggregates that can be incrementally updated. For the incrementally updatable class of summative aggregates, we propose an efficient cache mechanism that allows many user-queries to share accesses to the cached aggregates in a transparent way. | Keywords/Search Tags: | Rule, Aggregate, Propose, Cache, Data, User | | Related items |
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