Querying several conflictual databases
نویسندگان
چکیده
This paper addresses the problem of querying several databases considered as a whole. Assuming that the different databases share a common data description language, the problem that raises is to consistently answer queries even if the database contents are contradictory. The main contribution of this paper is the specification of a query-evaluator for answering closed and open queries addressed to several databases. For doing so, we first specify a query-evaluator, in logic, which assumes that the databases are propositional ones and do not contain disjonctions. Then we extend it to first-order databases defined by an extensional part (sets of positive or negative facts) and an intensional part (sets of first order clauses). We also show that the query-evaluator corresponds to a majority merging of the databases.
منابع مشابه
Logical and Semantic Database Integration
Two fundamental approaches for database integration exist: the data warehouse approach attempts to physically merge data sets from several source databases, whereas database federations simultaneously query source databases online. In this paper a database federation approach based on two components will be introduced. The MARGBench (Freier et al. 1999) is a system which, among other features, ...
متن کاملIssues in Querying Multi-media Databases
Introduction The amount of information available to users, especially in the web, is growing exponentially month by month. To nd useful information in the web, users normally have to rely on some sort of keyword matching searches, and/or navigate their way through the list of pointers to objects in diierent data repositories. This is not enough to satisfy the needs of the ever more sophisticate...
متن کاملQuerying Ontology Based Databases - The OntoQL Proposal
Several approaches for storing ontologies and their instances in databases have been proposed. As a consequence, the need of defining languages to query such ontology based databases (OBDB) appeared. In this paper, we present OntoQL, an ontology query language designed for OBDB databases. This paper particulary emphasizes on the language constructs. Several query examples showing the interest o...
متن کامل(Inductive) Querying Environment for Predictive Clustering Trees
Inductive databases tightly integrate databases with data mining. Besides data, an inductive database also stores models that have been obtained by running data mining algorithms on the data. By means of a querying environment, the user can query the database and retrieve particular models. In this paper, we propose such a querying environment. It can be used for building new models and for sea...
متن کاملDesign and Analysis of Querying Encrypted Data in Relational Databases
Security and privacy concerns as well as legal considerations force many companies to encrypt the sensitive data in databases. However, storing the data in an encrypted format entails non-negligible performance penalties while processing queries. In this paper, we address several design issues related to querying encrypted data in relational databases. Based on our experiments, we propose new a...
متن کامل