A useful logical semantics of UML for querying and checking UML class diagram

Date du colloque : 01/2009International audienc

Using UML Class Diagram as a Knowledge Engineering Tool

Date du colloque : 05/2000International audienc

Cohérence des données de bases RDF en évolution constante

National audienc

Aperçus de recherche : interroger efficacement un ensemble de bases RDF

In the context of information retrieval in the Web of Data, we propose a kind of compact version of a RDF triplestore, that acts as an overview on this base of RDF triples. An overview is not only more compact that the initial triplestore, but also SPARQL can be used on it. An overview is built in such a way that if a SPARQL query on overview has no result, then there is no result too to this query into the initial triplestore. So, querying overviews is a more efficient solution than querying the whole triplestores when the query has often no result from these RDF databases. It is usually the case when a user query triplestores on the web of data. Our solution has been evaluated using RDF bases extracted from DBPedia and queries extracted either from the most common used on DBPedia or because of their resolution complexity

Une synthèse des modèles de représentation des connaissances à base de Graphes Conceptuels et OWL

Nous présentons et comparons deux approches de modélisation, formelles et concrètes, pour représenter et manipuler des connaissances d’un domaine. Le modèle des graphes conceptuels permet de modéliser des connaissances en terme de graphes, basés sur un support. Cette approche de modélisation est intensionnelle, est munie d’une sémantique en logique du premier ordre, et fait l’hypothèse d’un monde fermé pour ses raisonnements. Le langage OWL permet de décrire des ontologies et des faits sur le Web, suivant une approche de modélisation extensionnelle. Il possède une sémantique issue des logiques de descriptions, et fait l’hypothèse d’un monde ouvert pour ses raisonnements

Conceptual Graphs and Datatypes

Datatypes, like numbers or strings, are widely used in Knowledge Representation (e.g. in RDF(S)/OWL or UML languages). The usual model of simple conceptual graphs does not support datatypes. Some extensions of conceptual graphs have been proposed for using datatypes, however these extensions often wander from initial model of conceptual graphs by introducing for instance procedural relations between nodes. This paper proposes a datatype extension for the simple conceptual graph model. Our contribution is threefold. First, we allow the use of datatypes for typing concept nodes. Second, we define two families of conceptual graphs: factual graphs and query graphs, both close to initial model. Factual graph is used to represent factual knowledge, including values of datatypes. Query graph may contain concept nodes that represent conditional queries on values of datatypes; these conditions are expressed by regular operators on datatypes. Third, we adapt projection to operate from a query graph to a factual graph

Transition-based system

Date du colloque : 09/2012International audienc

Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean

International audienceDue to the low atmospheric input of phosphate into the open ocean, it is one of the key nutrients that could ultimately control primary production and carbon export into the deep ocean. The observed trend over the last 20 years has shown a decrease in the dissolved inorganic phosphate (DIP) pool in the North Pacific gyre, which has been correlated to the increase in di-nitrogen (N2) fixation rates. Following a NW-SE transect, in the Southeast Pacific during the early austral summer (BIOSOPE cruise), we present data on DIP, dissolved organic phosphate (DOP) and particulate phosphate (PP) pools along with DIP turnover times (TDIP) and N2 fixation rates. We observed a decrease in DIP concentration from the edges to the centre of the gyre. Nevertheless the DIP concentrations remained above 100 nmol L-1 and T DIP was more than 6 months in the centre of the gyre; DIP availability remained largely above the level required for phosphate limitation to occur and the absence of Trichodesmium spp and low nitrogen fixation rates were likely to be controlled by other factors such as temperature or iron availability. This contrasts with recent observations in the North Pacific Ocean at the ALOHA station and in the western Pacific Ocean at the same latitude (DIAPALIS cruises) where lower DIP concentrations (-1) and T DIP 2 fixation rates and possibly carbon dioxide sequestration, if the primary ecophysiological controls, temperature and/or iron availability, were alleviated