Document Type


Publication Date

Spring 1997


The construction and maintenance of data warehouses (views) in large-scale environments composed of numer- ous distributed and evolving information sources (ISs) such as the WWW has received great attention recently Such environments are plagued with changing information because ISs tend to continuously evolve by modifying not only their content but also their query capabilities and interface and by joining or leaving the environment at any time We are the first to introduce and address the problem of capability (schema) changes of ISs while previous work in this area such as incremental view maintenance has mainly dealt with data changes at ISs In this paper we outline our solution approach to this challenging new problem of how to adapt views in such evolv- ing environments We identify a new view adaptation problem for view evolution in the context of ISs capability changes which we call View Synchronization We also outline the Evolvable View Environment (EVE) approach that we propose as framework for solving the view synchronization problem along with our decisions concerning the key design issues surrounding EVE The main contributions of this paper are: we provide an E-SQL view definition language with which the view definer can direct the view evolution process we introduce a model for in- formation source description which allows a large class of ISs to participate in our system dynamically we formally define what constitutes a legal view rewriting we develop replacement strategies for affected view components which can be shown to be correct and we provide a set of view synchronization algorithms A prototype of our EVE system has successfully been built using Java JDBC Oracle and MS Access; and is currently running in the CS Department at WPI