---------- Forwarded Message ---------- Subject: Content of JDM Vol. 12 No. 4 Date: Thu, 6 Sep 2001 01:43:45 -0500 From: Keng Siau ksiau@UNLNOTES.UNL.EDU To: ISWORLD@LISTSERV.HEANET.IE

The contents of the latest issue of:

Journal of Database Management (JDM) Official publication of the Information Resources Management Association Vol 12 #4, October-December 2001 Editor: Keng Siau, University of Nebraska-Lincoln

RESEARCH PAPERS:

ARTICLE ONE:

An Adaptive Probe-Based Technique to Optimize Join Queries in Distributed Internet Databases Latifur Khan University of Texas at Dallas, USA

Dennis McLeod, and Cyrus Shahabi University of Southern California, Los Angeles, USA

An adaptive probe-based optimization technique is developed and demonstrated in the context of an Internet-based distributed database environment. More and more common are database systems, which are distributed across servers communicating via the Internet where a query at a given site might require data from remote sites. Optimizing the response time of such queries is a challenging task due to the unpredictability of server performance and network traffic at the time of data shipment; this may result in the selection of an expensive query plan using a static query optimizer. We constructed an experimental setup consisting of two servers running the same DBMS connected via the Internet. Concentrating on join queries, we demonstrate how a static query optimizer might choose an expensive plan by mistake. This is due to the lack of a priori knowledge of the run-time environment, inaccurate statistical assumptions in size estimation, and neglecting the cost of remote method invocation. These shortcomings are addressed collectively by proposing a probing mechanism. Furthermore, we extend our mechanism with an adaptive technique that detects sub-optimality of a plan during query execution and attempts to switch to the cheapest plan while avoiding redundant work and imposing little overhead. An implementation of our run-time optimization technique for join queries was constructed in the Java language and incorporated into an experimental setup. The results demonstrate the superiority of our probe-based optimization over a static optimization.

ARTICLE TWO:

A Metadata Oriented Architecture for Building Datawarehouse

Heeseok Lee, Taehun Kim, and Jongho Kim Korea Advanced Institute of Science and Technology, Korea

Data warehouse is an intelligent store of data that can aggregate vast amounts of information. A metadata is critical for implementing data warehouse. Therefore, integrating data warehouse with its metadata offers a new opportunity to create a more adaptive information system. This paper proposes a metadata-oriented data warehouse architecture that consists of seven components: legacy system, extracting software, operational data store, data warehouse, data mart, application, and metadata. A taxonomy for dataflow and metaflow is proposed for better understanding of the architecture. In addition, a metadata schema is built within the framework of the seven components. The architecture with its metadata component is applied to a real-life data warehouse for a large medical center in order to illustrate its practical usefulness.

ARTICLE THREE:

The Development of Ordered SQL Packages to Support Data Warehousing

WILFRED ng Hong Kong University of Science and Technology, Hong Kong

MARK LEVENE University of London, UK

Data warehousing is a corporate strategy that needs to integrate information from several sources of separately developed Database Management Systems (DBMSs). A future DBMS of a data warehouse should provide adequate facilities to manage a wide range of information arising from such integration. We propose that the capabilities of database languages should be enhanced to manipulate user-defined data orderings, since business queries in an enterprise usually involve order. We extend the relational model to incorporate partial orderings into data domains and describe the ordered relational model. We have already defined and implemented a minimal extension of SQL, called OSQL, which allows querying over ordered relational databases. One of the important facilities provided by OSQL is that it allows users to capture the underlying semantics of the ordering of the data for a given application. Herein we demonstrate that OSQL aided with a package discipline can be an effective means to manage the inter-related operations and the underlying data domains of a wide range of advanced applications that are vital in data warehousing, such as temporal, incomplete and fuzzy information. We present the details of the generic operations arising from these applications in the form of three OSQL packages called: OSQL_TIME, OSQL_INCOMP and OSQL_FUZZY.

ARTICLE FOUR:

Issues in Transaction-Time Temporal Object Database Systems

Kjetil Nørvåg Norwegian University of Science and Technology, Norway

Object database systems (ODBs) are an attractive alternative to relational database systems, especially in application areas where the modeling power or performance of relational database systems is insufficient. These applications typically maintain large amounts of data. Frequently, some of the data is temporal data. For the temporal data, the whole history of the individual objects is kept, and data is never deleted. The area of temporal ODBs is still immature, and there are many design issues that need to be solved in order to be able to achieve the desired performance. In this paper, we discuss some temporal ODB research issues and possible solutions related to object storage, object management, main memory buffering, and language bindings.

***************************************************************************** ********************************** For full copies of the above articles, check this issue of the Journal of Database Management in your institution's library. ***************************************************************************** **********************************

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