The construction and maintenance of data warehouses (views) in large-scale environments composed of numerous 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 schema changes of ISs, while previous work in this area, such as incremental view maintenance, has mainly dealt with data changes at ISs. We outline our solution approach to this challenging new problem of how to adapt views in such evolving environments. We identify a new view adaptation problem for view evolution in the context of ISs schema 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: 1) we provide an E-SQL view definition language with which the view definer can direct the view evolution process, 2) we introduce a model for information source description which allows a large class of ISs to participate in our system dynamically, 3) we formally define what constitutes a legal view rewriting, 4) we develop replacement strategies for affected view components which are designed to meet the preferences expressed by E-SQL, 5) we prove the correctness of the replacement strategies, and 6) we provide a set of view synchronization algorithms based on those strategies. A prototype of our EVE system has successfully been built using Java, JDBC, Oracle, and MS Access.

Powerful solutions enabling interoperability must allow applications to evolve and the requirements of shared databases to change, while minimizing such changes on other integrated applications. Several approaches have been proposed to make interoperability possible by using object-oriented techniques. These approaches may generate a large number of schema versions over time, resulting in an excessive build-up of classes and underlying object instances, not all being necessarily still in use. This results in degradation of system performance due to the view maintenance and the storage overhead costs. In this paper, we address the problem of removing obsolete view schemas. We characterize four potential problems of schema consistency that could be caused by the removal of a single derived class. We demonstrate that schema version removal is sensitive to the order in which individual classes are processed, and present a formal dependency model that captures all dependencies between classes as logic clauses and manipulates them to make decisions on class deletions and non-deletions while guaranteeing the consistency of the schema. We have also developed and proven consistent a dependency graph (DG) representation of the formal model. Lastly, we present a cost model for evaluating alternative removal patterns on a DG to assure selection of the optimal solution. The proposed techniques have been implemented in our Schema View Removal (SVR) tool. Lastly, we report experimental findings for applying our techniques for consistent schema version removal on the MultiView/TSE (Transparent Schema Evolution) system.

Query rewriting with relaxed semantics has been proposed as a means of retaining the validity of a data warehouse (i.e., materialized queries) in a changing environment. Attributes in the query interface can be classified as essential or dispensable (if it cannot be retained) according to the query definer's preferences. Similarly, preferences for query extent can be specified, for example, to indicate whether a subset of the original result is acceptable or not. The paper discusses the trade-off between quality and cost of query rewriting.

Supporting independent ISs and integrating them in distributed data warehouses (materialized views) is becoming more important with the growth of the WWW. However, views defined over autonomous ISs are susceptible to schema changes. In the EVE project we are developing techniques to support the maintenance of data warehouses defined over distributed dynamic ISs [5, 6, 7]. The EVE system is the first to allow views to survive schema changes of their underlying ISs while also adapting to changing data in those sources. EVE achieves this is 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 definition 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.

Large information spaces such as the WWW face the problem of how to maintain data warehouses (views) defined over information sources (ISs) whenever capabilities of these ISs change. We have developed a novel solution approach to address this problem, called the evolvable view environment (EVE). In EVE, knowledge of both the capabilities of as well as (partial) containment relationships between ISs is collected in a meta knowledge base (MKB). We describe the meta knowledge management problem and focus on issues related to the MKB evolution process. The contributions of this paper are threefold: 1) formally define consistency criteria for the MKB evolution process; 2) use PC constraint evolution to demonstrate our MKB evolution process; and 3) discuss techniques of keeping the MKB as powerful as possible by deriving and preserving minimal implicit knowledge from the affected explicit meta knowledge, before retracting the latter.

We describe the design and implementation of a scientific database for the map assembly tasks performed by the geneticists at the University of Michigan Human Genome Center. Our system manages complex genomic data and supports the automation of the associated map assembly tasks. For the former, we present a genomic object model that integrates both experimental and derived data. For the latter, we describe operators to automate some of the analysis steps. To develop a framework for implementing our rule-based approach to physical mapping, we have designed and implemented an active object-oriented database (OODB) system, called Crystal, on GemStone. Crystal seamlessly integrates inference capabilities with complex object modeling and other typical database capabilities as required for physical mapping. We also discuss the implementation of a physical map assembly tool on top of Crystal. In conclusion, we provide a walk-through example that demonstrates how our approach can be used to effectively support physical contig assembly.>

Article An information model for genome map representation and assembly Share on Authors: A. J. Lee Department of EECS, University of Michigan, Ann Arbor, Ann Arbor, MI Department of EECS, University of Michigan, Ann Arbor, Ann Arbor, MIView Profile , E. A. Rendensteiner Department of EECS, University of Michigan, Ann Arbor, Ann Arbor, MI Department of EECS, University of Michigan, Ann Arbor, Ann Arbor, MIView Profile , S. Thomas Information Technology and Networking, University of Michigan Medical Center, Human Genome Center, 2570C MSRB II Information Technology and Networking, University of Michigan Medical Center, Human Genome Center, 2570C MSRB IIView Profile , S. Lafortune Department of EECS, University of Michigan, Ann Arbor, Ann Arbor, MI Department of EECS, University of Michigan, Ann Arbor, Ann Arbor, MIView Profile Authors Info & Claims CIKM '93: Proceedings of the second international conference on Information and knowledge managementDecember 1993 Pages 75–84https://doi.org/10.1145/170088.170107Published:01 December 1993 5citation1,221DownloadsMetricsTotal Citations5Total Downloads1,221Last 12 Months0Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access