Answering queries using views: A survey

Halevy, Alon

doi:10.1007/s007780100054

Cited by 1,078 publications

(720 citation statements)

References 84 publications

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“…3.5.3 above. Here, a query q can be evaluated against an integrated set of data D sources to produce a result r, where the integration arises from a set of mappings v over the mediated model m obtained from D. In a globalas-view approach [28], the query q posed against the mediated schema arising from the integration of D is translated using the mapping elements in v over m into single-source queries (see [28] for a survey of the techniques involved). Thus, if D = {d 1 , d 2 }, then, broadly speaking, two operations are issued, viz., r 1 := evalQ(d 1 , q 1 ) and r 2 := evalQ(d 2 , q 2 ) using v over m to derive both q 1 and q 2 from q, and, on the way back, r from r 1 and r 2 .…”

Section: Data Source Operationsmentioning

confidence: 99%

“…This problem, under the label of data integration [5,20,30,42], has been the focus of attention for more than fifteen years. Much progress has been made and several enduring contributions can be discerned such as the idea of mediator-wrapper architectures and techniques for view-based query rewriting that allow a query that is posed against an integration schema to be rewritten as a set of separate queries against the many independent, remote sources it draws data from [28]. Most of these techniques are grounded on two basic capabilities: the first is the ability to perform a semantic matching operation between two sources (typically at both schema and instance levels) that ultimately yields semantic correspondences between them; the second is the ability to derive from these correspondences a semantic mapping, i.e., ultimately, an executable expression that can correctly populate concepts in one schema with instances drawn from concepts in the other.…”

Section: Introductionmentioning

confidence: 99%

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A Functional Model for Dataspace Management Systems

Hedeler

Fernandes

Belhajjame

et al. 2013

Advanced Query Processing

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Dataspace management systems (DSMSs) hold the promise of pay-asyou-go data integration. We describe a comprehensive model of DSMS functionality using an algebraic style. We begin by characterizing a dataspace life cycle and highlighting opportunities for both automation and user-driven improvement techniques. Building on the observation that many of the techniques developed in model management are of use in data integration contexts as well, we briefly introduce the model management area and explain how previous work on both data integration and model management needs extending if the full dataspace life cycle is to be supported. We show that many model management operators already enable important functionality (e.g., the merging of schemas, the composition of mappings, etc.) and formulate these capabilities in an algebraic structure, thereby giving rise to the notion of the core functionality of a DSMS as a many-sorted algebra. Given this view, we show how core tasks in the dataspace life cycle can be enacted by means of algebraic programs. An extended case study illustrates how such algebraic programs capture a challenging, practical scenario.

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Section: Data Source Operationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Functional Model for Dataspace Management Systems

Hedeler

Fernandes

Belhajjame

et al. 2013

Advanced Query Processing

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“…The key principle that we use is reducing the mapping compilation problem to that of finding exact rewritings of queries using views [21].…”

Section: View Generation Algorithmmentioning

confidence: 99%

Compiling mappings to bridge applications and databases

Melnik

Adya

Bernstein

2008

ACM Trans. Database Syst.

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Translating data and data access operations between applications and databases is a longstanding data management problem. We present a novel approach to this problem, in which the relationship between the application data and the persistent storage is specified using a declarative mapping, which is compiled into bidirectional views that drive the data transformation engine. Expressing the application model as a view on the database is used to answer queries, while viewing the database in terms of the application model allows us to leverage view maintenance algorithms for update translation. This approach has been implemented in a commercial product. It enables developers to interact with a relational database via a conceptual schema and an object-oriented programming surface. We outline the implemented system and focus on the challenges of mapping compilation, which include rewriting queries under constraints and supporting non-relational constructs.

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“…This service can be realized via query rewriting: the query over the global ontology can be rewritten into a query that is then evaluated over the local sources [10]. Calvanese et al [5] showed that query rewriting in global-as-view II systems-that is, systems in which concepts and roles from the global ontology are mapped to the local sources by a query over one or more sources [15]-can be solved in two stages.…”

Section: Introductionmentioning

confidence: 99%

Rewriting Conjunctive Queries over Description Logic Knowledge Bases

Perez-Urbina

Motik

Horrocks

2008

Semantics in Data and Knowledge Bases

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Abstract. We consider the problems of conjunctive query answering and rewriting for information integration systems in which a Description Logic ontology is used to provide a global view of the data. We present a resolution-based query rewriting algorithm for DL-Lite + ontologies, and use it to show that query answering in this setting is NLogSpacecomplete with respect to data complexity. We also show that our algorithm produces an optimal rewriting when the input ontology is expressed in the language DL-Lite. Finally, we sketch an extended version of the algorithm that would, we are confident, be optimal for several DL languages with data complexity of query answering ranging from LogSpace to PTime-complete.

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Answering queries using views: A survey

Cited by 1,078 publications

References 84 publications

A Functional Model for Dataspace Management Systems

A Functional Model for Dataspace Management Systems

Compiling mappings to bridge applications and databases

Rewriting Conjunctive Queries over Description Logic Knowledge Bases

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