We define mixed fragmentation as a process of simultaneously applying the horizontal and vertical fragmentation on a relation. It can be achieved in one of two ways: by performing horizontal fragmentation followed by vertical fragmentation or by performing vertical fragmentation followed by horizontal fragmentation. The need for mixed fragmentation arises in distributed databases because database users usually access subsets of data which are vertical and horizontal fragments of global relations and there is a need to process queries or transactions that would access these fragments optimally. We present algorithms for generating candidate vertical and horizontal fragmentation schemes and propose a methodology for distributed database design using these fragmentation schemes. When applied together these schemes form a grid. This grid consisting of cells is then merged to form mixed fragments so as to minimize the number of disk accesses required to process the distributed transactions....

The world-wide web (WWW) is often considered to be the world’s largest database and the eXtensible Markup Language (XML) is then considered to provide its datamodel. Adopting this view we have to deal with a distributed database. This raises the question, how to obtain a suitable distribution design for XML documents. In this paper horizontal and vertical fragmentation techniques are generalised from the relational datamodel to XML. Furthermore, splitting will be introduced as a third kind of fragmentation. Then it is shown how relational techniques for defining reasonable fragments can be applied to the case of XML. 1

Abstract. A challenging question is how XML can be used to support distributed databases. This leads to the problem of how to obtain a suitable, cost-efficient distribution design for XML documents. In this paper we sketch a heuristic approach to minimise query costs for the case of horizontal fragmentation. The approach is based on a cost model that takes the complex structure of queries on XML documents into account. We show that the minimisation of transportation costs is decisive, and that this can be achieved locally by either accepting or rejecting a horizontal fragmentation with a simple predicate that arises from one of the most frequent queries. 1

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Abstract — Performance of proxy caches for database federations that serve a large number of users is crucially dependent on its physical design. Current techniques, automated or otherwise, for physical design depend on the identification of a representative workload. In proxy caches, however, such techniques are inadequate since workload characteristics change rapidly. This is remarkably shown at the proxy cache of SkyQuery, an Astronomy federation, which receives a continuously evolving workload. We present novel techniques for automated physical design that adapt with the workload and balance the performance benefits of physical design decisions with the cost of implementing these decisions. These include both competitive and incremental algorithms that optimize the combined cost of query evaluation and making physical design changes. Our techniques are general in that they do not make assumptions about the underlying schema nor the incoming workload. Preliminary experiments on the TPC-D benchmark demonstrate significant improvement in response time when the physical design continually adapts to the workload using our online algorithm compared with offline techniques. I.

. Within the framework of the data warehouse design<E-345> methodology we are developing, in this paper we investigate the problem<E-338> of vertical fragmentation of relational views aimed at minimizing the<E-358> global query response time. Each view includes several measures which,<E-344> within the workload, are seldom requested together; thus, the system<E-343> performance may be increased by partitioning the views to be materialized<E-324> into smaller tables. On the other hand, drill-across queries involve measures<E-336> taken from two or more views; in this case the access costs may be decreased<E-335> by unifying these views into larger tables. Within the data warehouse<E-331> context, the presence of redundant views makes the fragmentation problem<E-338> more complex than in traditional relational databases since it requires to<E-362> decide on which views each query should be executed. After formalizing the<E-358> fragmentation problem as a 0-1 integer linear programming pr...

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Because of data proliferation, efficient access methods and data storage techniques have become increasingly critical to maintain an acceptable query response time. One way to improve query response time is to reduce the number of disk I/Os by partitioning the database vertically (attribute clustering) and/or horizontally (record clustering). A clustering is optimized for a given set of queries. However in dynamic systems the queries change with time, the clustering in place becomes obsolete, and the database needs to be re-clustered dynamically. In this paper we discuss an efficient algorithm 1 for attribute clustering that dynamically and automatically generate attribute clusters based on closed item sets mined from the attributes sets found in the queries running against the database. 1.

Abstract. We introduce AdaptPD, an automated physical design tool that improves database performance by continuously monitoring changes in the workload and adapting the physical design to suit the incoming workload. Current physical design tools are offline and require specification of a representative workload. AdaptPD is “always on ” and incorporates online algorithms which profile the incoming workload to calculate the relative benefit of transitioning to an alternative design. Efficient query and transition cost estimation modules allow AdaptPD to quickly decide between various design configurations. We evaluate AdaptPD with the SkyServer Astronomy database using queries submitted by SkyServer’s users. Experiments show that AdaptPD adapts to changes in the workload, improves query performance substantially over offline tools, and introduces minor computational overhead. 1

This paper describes MoonBase, a multimedia database system being developed for new emerging multimedia applications. MoonBase provides a complete system solution to manage diverse multimedia technologies and integrate multimedia islands-of-information. MoonBase is an extensible federated relational database coordinator that non-intrusively adds multimedia capabilities to existing relational database management systems for mission-critical environments. MoonBase uses a parallel multimedia object server called Prospector, to store and manipulate multimedia objects. Prospector is a multi-purpose object server that internally builds upon Bell Labs' EOS transactional object manager. Prospector executes User Defined Functions (UDFs) in a parallel environment which allows high performance content-analysis and complex operations to be performed on large databases of (multimedia) objects. In this paper, we describe the global architectures of Moonbase and Prospector; the SQL3 Abstract Data Typ...