Nicolas Spyratos

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A database view is a portion of the data structured in a way suitable to a specific application. Updates on views must be translated into updates on the underlying database. This paper studies the translation process in the relational model. The procedure is as follows: first, a &#8220;complete&#8221; set of updates is defined such that<list><item>together(More)
The notion of context appears in computer science, as well as in several other disciplines, in various forms. In this paper, we present a general framework for representing the notion of context in information modeling. First, we define a context as a set of objects, within which each object has a set of names and possibly a reference: the reference of the(More)
Views over databases have regained attention in the context of data warehouses, which are seen as materialized views. In this setting, efficient view maintenance is an important issue, for which the notion of self-maintainability has been identified as desirable. In this paper, we extend the concept of self-maintainability to (query and update) independence(More)
Preference queries are crucial for various applications (e.g. digital libraries) as they allow users to discover and order data of interest in a personalized way. In this paper, we define preferences as preorders over relational attributes and their respective domains. Then, we rely on appropriate linearizations to provide a natural semantics for the block(More)
This paper describes the personalisation services designed for self e-learning networks in the SeLeNe project. A self e-learning network consists of web-based learning objects that have been made available to the network by its users, along with metadata descriptions of these learning objects and of the network’s users. The proposed personalisation(More)
In this report, we propose a simple data model for the composition and metadata management of learning objects (LOs) in a distributed setting that we call a Self-eLearning Network, or SeLeNe for short. The model features an abstract definition of LO, as well as operations that allow to compose new LOs from simpler ones, and to query a database of LOs spread(More)
We study conjunctive queries that combine information from multiple sources. The need for combining information is manifest for instance in multimedia systems. It has recently been recognized that query semantics for these systems should be based on some quantitative model, such as fuzzy logic. Further complications arise, however, since the semantics used(More)
We propose a model for providing integrated and unified access to multiple information sources. Each information source comprises two parts: (a) an ontology i.e. a set of terms structured by a subsumption relation, and (b) a database that stores objects under the terms of the ontology. We assume that the objects of interest belong to an underlying domain(More)