Adding Conflict Resolution Features to a Query Language for Database Federations

Sattler, Kai-Uwe; Conrad, Stefan; Saake, Gunter

doi:10.3127/ajis.v8i1.262

Cited by 26 publications

(20 citation statements)

References 21 publications

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“…In the following we will focus on two approaches which are implemented as part of the multidatabase system FRAQL query processor [SCS00]: LIMIT FIRST and LIMIT SAMPLE. Both are extensions to the standard SQL SELECT statement:…”

Section: Related Workmentioning

confidence: 99%

“…This value is used to adjust the histogram for a.account no (denoted as hist (account no) ) by reducing the height of each bucket assuming independence of the attributes: ½ Ù Ø´ µ Ù Ø´ µ £ × Ð ¼¼¼ Next, the histogram hist (cust id) for´ º» µ º» is calculated as shown above, whereas the stop operator is ignored for the moment. The cardinality of the final result set at the root of the operator tree is equal to the sum of the heights of all buckets of this histogram: A special treatment is required for histograms of relations containing attributes which are transformed by applying so-called mapping functions [SCS00] as part of the view definition. Because the mapping is implemented as a special query operator in the query plan the involved histogram also has to be mapped.…”

Section: Using Histograms For Estimating Stop Cardinalitiesmentioning

confidence: 99%

“…By means of multidatabase languages (e.g MSQL [GLRS93], SchemaSQL [LSS96], FRAQL [SCS00]) we have the tools at hand which are needed for querying across diverse data sources. Querying using multiple data sources usually produces complete result sets.…”

Section: Introductionmentioning

confidence: 99%

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Limiting Result Cardinalities for Multidatabase Queries Using Histograms

Sattler

Dunemann

Geist

et al. 2001

Lecture Notes in Computer Science

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Abstract.Integrating, cleaning and analyzing data from heterogeneous sources is often complicated by the large amounts of data and its physical distribution which can result in poor query response time. One approach to speed up the processing is to reduce the cardinality of results -either by querying only the first tuples or by obtaining a sample for further processing. In this paper we address the processing of such queries in a multidatabase environment. We discuss implementations of the query operators, strategies for their placement in a query plan and particularly the usage of histograms for estimating attribute value distributions and result cardinalities in order to parameterize the operators.

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Section: Related Workmentioning

confidence: 99%

Section: Using Histograms For Estimating Stop Cardinalitiesmentioning

confidence: 99%

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Limiting Result Cardinalities for Multidatabase Queries Using Histograms

Sattler

Dunemann

Geist

et al. 2001

Lecture Notes in Computer Science

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“…An integration relation is a view on other global relations combined by using operators like union, -join and outer join, which are extended by reconciliation functions for conflict resolution [19]. In addition, the standard SQL operations selection and projection are provided, too.…”

Section: Federation Layermentioning

confidence: 99%

“…These services are implemented by using the FRAQL language and query processor [19]. FRAQL is a query language for object-relational database federations.…”

Section: Federation Layermentioning

confidence: 99%

Federation services for heterogeneous digital libraries accessing cooperative and non-cooperative sources

Endig

Höding²,

Saake³

et al.

Proceedings 2000 Kyoto International Conference on Digital Libraries: Research and Practice

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Today, bibliographical information is kept in a vari MotivationThe integration of existing digital libraries and electronic catalogues of publications is considered as one of the main tasks in the digital library community [22]. Publishers, libraries and computer scientists engage in developing digital libraries and electronic catalogues in order to make the publications themselves (digital contents) and their accompanying meta-data (bibliographical data about the publications) available. In different libraries and catalogues various services based on the provided information are offered for certain area of research, for instance the ACM and IEEE digital libraries providing meta-data and full text for computer science in general and the DBLP (Computer Science Bibliography) service provide meta-data for the field of database research. Generally, the provided services differ in their quality, for instance full text versus bibliographical data, quantity and the associated cost model. Today, the integration of meta-data from the available heterogeneous sources and the identification of objects in this global scope are major problems for the integration of digital libraries. For the latter problem current developments in the WWW technology and probabilistic approaches for identifying same objects seem to be promising. New techniques to tackle the problem of meta-data integration were developed in the area of integration of information systems, such as federated database systems and mediator based architectures. The provision of a single point of access to bibliographical meta-data for the users would allow to look up publications more efficiently. Furthermore, the integration makes it possible to derive information about implicit relationships among data spread over various sources, for instance citation linking information.For the integration of bibliographical data various projects were started, and newly developed methods and technologies from the research area of federated databases and mediator systems were applied successfully. But some problems remained unsolved, because of the complexity resulting from the high level of heterogeneity regarding data representation, contents and interfaces. All approaches have a similar multi-tier architecture in common that provides adapters and/or wrappers for certain classes of sources to deal with interface heterogeneity and, depending on the approach, various issues of data representation. Due to the interface heterogeneity and varying levels of cooperativeness of data providers all of these approaches have their limitations.In this paper our approach for integrating heterogeneous digital libraries based on federation services will be presented, whereby both cooperative and noncooperative sources are taken into consideration. The remainder of this paper is structured as follows. In section 2 we give a short overview of related work. In section 3 we introduce an exemplary scenario for the integration of digital libraries in heterogeneous environ-

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Declarative Data Fusion – Syntax, Semantics, and Implementation

Bleiholder

Naumann

2005

Advances in Databases and Information Systems

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Adding Conflict Resolution Features to a Query Language for Database Federations

Cited by 26 publications

References 21 publications

Limiting Result Cardinalities for Multidatabase Queries Using Histograms

Limiting Result Cardinalities for Multidatabase Queries Using Histograms

Federation services for heterogeneous digital libraries accessing cooperative and non-cooperative sources

Declarative Data Fusion – Syntax, Semantics, and Implementation

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