Section: New Results

Scalable and Expressive Techniques for the Semantic Web

On the topic of efficient query answering methods for semantic-rich RDF data, we have obtained new fundamental results for the RDF Schema ontology language [25] and for a simple DL-Lite dialect [23] , [34] ; we presented our results in a tutorial at IEEE ICDE [10] and in an invited keynote at SEBD, the Italian Database conference [4] . A demonstration issued from this work was presented at VLDB [26] and at BDA, the French database conference [27] .

To help users get acquainted with large and complex RDF graphs, we have started to work on an approach for RDF graph summarization: a graph summary is a smaller RDF graph, often by several orders of magnitude, which preserves the core structural information of the original graph and thus allows to reason about several important graph property on a much more manageable structure. Our first results were presented in [17] and demonstrated at [29] and [30] . These results were also presented in the keynote of the Data Engineering and the Semantic Web workshop [5] .

On the related topic of analytical RDF schemas, we have published novel techniques for incrementally computing the result of an RDF analytical query (also known as “RDF cube”) out of the result of a previously computed RDF cube [31] . Such computations, commonly known as roll-up, drill-down etc. in the classical relational database setting, require novel solutions for RDF due to the heterogeneity of the graph structure.