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With the success of the semantic web infrastructures for storing and querying RDF data are gaining importance. A couple of systems are available now that provide basic database functionality for RDF data. Compared to modern database systems, RDF storage technology still lacks sophisticated optimization methods for query processing. Current work in this direction is mainly focussed on index structures...
Current Geographic Information Systems (GISs) are inadequate for performing spatial analysis, since they force users to formulate their often vague requests by means of crisp selection conditions on spatial data. In fact, SQL extended to support spatial analysis is becoming the de facto standard for GISs; however, it does not allow the formulation of flexible queries. Based on these considerations,...
In this paper we discuss access to object attributes in a multigranular temporal object-oriented data model that handles the expiration of dynamic attributes, according to the age of data and their granularity [4]. Different strategies can be applied, with respect to available data and to the preferences specified by the user on either accuracy or efficiency in executing a query. We devise some properties...
Fuzzy object-oriented data model is a fuzzy logic-based extension to object-oriented database model, which permits uncertain data to be explicitly represented. One of the proposed fuzzy object-oriented database models based on similarity relations is the FOOD model. Several kinds of fuzziness are dealt with in the FOOD model, including fuzziness between object/class and class/ superclass relations...
In the context of relational as well as deductive databases, correct and efficient integrity checking is a crucial issue, as, without any guarantee of data consistency, the answers to queries cannot be trusted. To be of any practical use, any method for integrity checking must support aggregates and arithmetic constraints, which are among the most widespread constructs in current database technology...
We present QBF (Query Broker Framework), a query evaluation framework that facilitates reuse and design of flexible query processors. QBF integrates existing optimization and execution mechanisms in a uniform way. It allows the use of multiple mechanisms to efficiently and adaptively evaluate queries according to application requirements. The smallest query evaluation unit built from QBF is called...
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