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Evolvable View Environment EVE: A Data Warehouse System Handling Schema and Data Changes of Distribu
| Content Provider | Semantic Scholar |
|---|---|
| Author | Rundensteiner, Elke A. Koeller, Andreas Zhang, Xiao-Dong Lee, Amy Junghyun Nica, Anisoara |
| Copyright Year | 1999 |
| Abstract | 1 Overview Supporting independent ISs and integrating them in distributed data warehouses (materialized views) is becoming more important with the growth of the WWW. However, views deened over autonomous ISs are susceptible to schema changes. In the EVE project we are developing techniques to support the maintenance of data warehouses deened over distributed dynamic ISs 6, 7, 8]. The EVE system is the rst to allow views to survive schema changes of their underlying ISs while also adapting to changing data in those sources. EVE achieves this in two steps: applying view query rewriting algorithms that exploit information about alternative ISs and the information they contain, and incrementally adapting the view extent to the view deenition changes. Those processes are referred to as view synchronization and view adaption, respectively. They increase the survivability of materialized views in changing environments and reduce the necessity of human interaction in system maintenance. Rundensteiner would like to thank our industrial sponsors, in particular, IBM for the IBM partnership award and for the IBM corporate fellowship for one of her graduate students. E-SQL or Evolvable-SQL is an extension of SQL that allows the view deener to express preferences for view evolution 6, 10, 7]. A user deening a view can specify what information is indispensable, what information is replaceable by similar information from other ISs, and whether a changing view extent is acceptable. Relaxed query semantics provided by E-SQL is the key to obtaining non-equivalent but useful query rewritings as it provides the EVE system with the exibility to evolve a view under schema changes in a controlled way while preserving the user's intended semantics. In order to enable view adaptation and rewrite view deenitions aaected by IS evolution, our system needs to be able to identify view component replacements from other ISs. Through a model for meta knowledge, we express relationships between ISs using constraints (e.g., agreeing data types, functional dependencies between attributes, extent overlaps between relations). These descriptions form an information pool that is critical in nding appropriate replacements for view components (i.e., attributes, relations, WHERE-conditions) when view deenitions become undeened. The meta knowledge about the information space is stored in our system in the Meta Knowledge Base (MKB) whereas E-SQL view deenitions are stored and maintained in theView Knowledge Base (VKB) as depicted in Figure 1. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://davis.wpi.edu/dsrg/EVE/PAPERS/ideas99-demo-camera.ps |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
