Alain Bidault

Bio: Alain Bidault is an academic researcher from University of Paris-Sud. The author has contributed to research in topics: Information integration & Formalism (philosophy). The author has an hindex of 2, co-authored 4 publications receiving 50 citations.

Repairing queries in a mediator approach

Abstract: In this paper, we study unsatisfiable queries posed to a mediator in an information integration system and expressed in the logical formalism of the information integration system PICSEL2 First, we characterise conflicts as the minimal causes of the unsatisfiability of a query Then, we produce its set of repairs: a repair is a query that does not generate any conflict and that has a common generalisation with the initial query and is semantically close to it

Similarity between queries in a mediator

Abstract: Answering queries on remote and heterogeneous sources is a complex task. Mediators provide techniques that exploit a domain ontology. To propose a cooperative approach to repair queries without answers, we introduce the notion of solution which is a query close to the user's query. We describe how ontologies can be used to evaluate the similarity of two predicates and then of two queries. The work presented has been developed in the PICSEL2 project. Examples come from the domain of tourism, the experimentation domain chosen for this project.

Finding Successful Queries in a Mediator Context

Abstract: In this paper, we study failing queries posed to a mediator in an information integration system and expressed in the logical formalism of the information integration system PICSEL1. First, we present the notion of concept generalisation in a concept hierarchy that is used to repair failing queries. Then, we address two problems arising while rewriting a query using views. The first problem concerns queries that cannot be rewritten due to a lack of sources, the second one concerns queries that have only unsatisfiable rewritings.

Preferences for queries in a mediator approach

Abstract: The problem of integrating relevant information obtained from multiple heterogeneous sources is a complex task, with which biologists are now faced. In this paper, we address the problem of querying biomedical databases in a mediator context. We propose to exploit the metadata of the sources to take into account user preferences. The mediator system we present is designed within a tractable logical framework. It allows both transparent and cooperative querying and makes it possible to keep track of the origins of the instances provided as answers. Our proposal is generic in that it is relevant not only for bioinformatics, but could also be applied to other domains for which metadata are available.

Fuzzy querying of incomplete, imprecise, and heterogeneously structured data in the relational model using ontologies and rules

Abstract: In this paper, we present a new method, called multiview fuzzy querying, which permits to query incomplete, imprecise and heterogeneously structured data stored in a relational database. This method has been implemented in the MIEL software. MIEL is used to query the Sym'Previus database which gathers information about the behavior of pathogenic germs in food products. In this database, data are incomplete because information about all possible food products and all possible germs is not available; data are heterogeneous because they come from various sources (scientific bibliography, industrial data, etc); data may be imprecise because of the complexity of the underlying biological processes that are involved. To deal with heterogeneity, MIEL queries the database through several views simultaneously. To query incomplete data, MIEL proposes to use a fuzzy set, expressing the query preferences of the user. Fuzzy sets may be defined on a hierarchized domain of values, called an ontology (values of the domain are connected using the a kind of semantic link). MIEL also proposes two optional functionalities to help the user query the database: i) MIEL can use the ontology to enlarge the querying in order to retrieve the nearest data corresponding to the selection criteria; and ii) MIEL proposes fuzzy completion rules to help the user formulate his/her query. To query imprecise data stored in the database with fuzzy selection criteria, MIEL uses fuzzy pattern matching.

Semantic integration in Xyleme: a uniform tree-based approach

Abstract: Xyleme is a huge warehouse integrating XML data of the Web. Xyleme considers a simple data model with data trees and tree types for describing the data sources, and a simple query language based on tree queries with boolean conditions. The main components of the data model are a mediated schema modeled by an abstract tree type, as a view of a set of tree types associated with actual data trees, called concrete tree types, and a mapping expressing the connection between the mediated schema and the concrete tree types. The first contribution of this paper is formal: we provide a declarative model-theoretic semantics for Xyleme tree queries, a way of checking tree query containment, and a characterization of tree queries as a composition of branch queries. The other contributions are algorithmic and handle the potentially huge size of the mapping relation which is a crucial issue for semantic integration and query evaluation in Xyleme. First, we propose a method for pre-evaluating queries at compile time by storing some specific meta-information about the mapping into map translation tables. These map translation tables summarize the set of all the branch queries that can be generated from the mediated schema and the set of all the mappings. Then, we propose different operators and strategies for relaxing queries which, having an empty map translation table, will have no answer if they are evaluated against the data. Finally, we present a method for semi-automatically generating the mapping relation.

Mediators over taxonomy-based information sources

Abstract: We propose a mediator model for providing integrated and unified access to multiple taxonomy-based sources. Each source comprises a taxonomy and a database that indexes objects under the terms of the taxonomy. A mediator comprises a taxonomy and a set of relations between the mediator’s and the sources’ terms, called articulations. By combining different modes of query evaluation at the sources and the mediator and different types of query translation, a flexible, efficient scheme of mediator operation is obtained that can accommodate various application needs and levels of answer quality. We adopt a simple conceptual modeling approach (taxonomies and intertaxonomy mappings) and we illustrate its advantages in terms of ease of use, uniformity, scalability, and efficiency. These characteristics make this proposal appropriate for a large-scale network of sources and mediators.

OntoRefiner, a user query refinement interface usable for Semantic Web Portals.

Abstract: We present a user interface, the OntoRefiner system, for helping the user to navigate numerous retrieved documents after a search querying a semantic portal which integrates a very important number of documents. Retrieved answers are filtered and the user could be provided only with the answers which are, according to him, the most relevant. The refinement process is based on two technologies, dynamic clustering close to Galois lattice structure combined to the use of a domain ontology. The Galois lattice structure provides a sound basis for the query refinement process. However, its construction as a whole is a very costly process. So, we propose an approach based on the use of a domain ontology, avoiding the construction of the whole Galois lattice. In the paper, we present the algorithm and experimental results.