Title : Generating Social Graphs for RDF Benchmarks

Presenter Peter Boncz
Abstract Benchmarking graph-oriented database workloads and graph-oriented database systems are increasingly becoming relevant in analytical Big Data tasks, such as social network analysis. In graph data, structure is not mainly found inside the nodes, but especially in the way nodes happen to be connected, i.e. structural correlations. Because such structural correlations determine join fan-outs experienced by graph analysis algorithms and graph query executors, they are an essential, yet typically neglected, ingredient of synthetic graph generators. To address this, we present S3G2: a Scalable Structure-correlated Social Graph Generator. This graph generator creates a synthetic social graph, containing non-uniform value distributions and structural correlations, and is intended as a testbed for scalable graph analysis algorithms and graph database systems. We generalize the problem to decompose correlated graph generation in multiple passes that each focus on one so-called correlation dimension; each of which can be mapped to a MapReduce task. We show that using S3G2 can generate social graphs that (i) share well-known graph connectivity characteristics typically found in real social graphs (ii) contain certain plausible structural correlations that influence the performance of graph analysis algorithms and queries, and (iii) can be quickly generated at huge sizes on common cluster hardware.
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Title : Expert vs. non-expert annotations of fiction films: an experiment using a tagging game

Presenter Liliana Melgar
Abstract Most film archives are making their content available online. This is the case of the European Film Gateway (EFG), an aggregator of films and film related documents from 16 European film archives and cinémathèques, which provides this content to Europeana. This presentation will show the details of an experiment design using Waisda?, which provides a game setting for both film experts and novices to tag few videos coming from this Gateway. The resulting tags will be analyzed, in order to understand their nature, and possibly suggest which ways could be more suitable for using social tagging for accessing or browsing fiction films in the audiovisual heritage domain. This work is being done together with the Web and Media Group, as part of my three month internship at VU. The presentation is done with the purpose of kindly asking you for feedback and general comments on the experiment design. Please bring your own laptop if you want to play the game!