Differential Evaluation of Continual Queries

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  • Technical report TR95-17. Information Superhighway environments such as the Internet have brough us ready access to large amounts of information. However, Internet data is notoriously unorganized and autonomously managed in a distributed fashion. Large scale information monitoring in the Internet environment requires support beyond traditional database techniques. Two of the key issues are the increasing reward in monitoring a fast growing information base and the similarly increasing processing cost. To improve the expressiveness of queries for information monitoring, we define continual queries as a useful tool for monitoring of updated information. Continual queries are standing queries that monitor the source data and notify the users whenever new data matches the query. In addition to periodic refresh, continual queries include Epsilon Transaction concepts to allow users to specify query refresh based on the magnitude of updates. To support effiecient processing of continual queries, we propose a differential re-evaluation algorithm (DRA), which exploits the structure and information contained in both the query expressions and the database update operations. The DRA design can be seen as a synthesis of previous research on differential files, incrementala view maintenance, and active databases. | TRID-ID TR95-17

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    Attribution 3.0 International