Abstract : The Resource Description Framework (RDF) is the W3C's graph data model for Semantic Web applications. We study the problem of RDF graph summarization: given an input RDF graph G, find an RDF graph G’ which summarizes G as accurately as possible, while being possibly orders of magnitude smaller than the original graph. Our summaries are aimed as a help for query formulation and optimization; in particular, querying a summary of a graph should reflect whether the query has some answers against this graph. We introduce two summaries: a baseline which is compact and simple and satisfies certain accuracy and representativeness properties, but may oversimplify the RDF graph, and a refined one which trades some of these properties for more accuracy in representing the structure. The demonstration will allow the audience to compute such summaries out of a large variety of datasets, and explore their usage for data exploration and query optimization.