Hasso-Plattner-Institut
 
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Semantic Technologies

In recent years the Semantic Web has emerged as one of the most essential achievements for the future of the World Wide Web (WWW). Semantic Web technology extends the WWW but also enables to improve applications which are related to other fields such as communication, information, knowledge, media, and interaction technologies. Semantic Web provides not just new technologies and tools but also new paradigms and ways of thinking, to make information processing more efficient and more structured.

Our research is focussed on the devolpment and improvement of 'semantically supported multimedia retrieval and search technologies'.

Table of Contents

  • Current News
  • Prior Events and Activities
  • Research Topics
  • Research Team
  • Former Team Members
  • Teaching
  • Supervised Master Theses
  • Projects and Partners
  • In the Media
  • Recent Publications

Research Topics

  • (1) Semantic Multimedia
  • (2) Linked Data Engineering and Applications
  • (3) Semantically enhanced Information Retrieval (Semantic Search)
  • (4) Knowledge Mining and Ontological Engineering
  • (5) Semantically enriched e-Learning Applications

Job Offers

Research Team

Former Team Members

  • Dr. Olaf Hartig (PostDoc)
  • Dinesh Reddy, M.Sc.
  • Tamara Bobic, M.Sc.
  • Dipl.-Inf. Katarina Birghan
  • Bernhard Quehl, M.Sc.
  • Dr. Nadine Steinmetz
  • Dr. Haojin Yang
  • Dipl.-Inf. Lina Wolf
  • Dipl.-Dokumentar Johannes Hercher
  • Joscha Jäger, M.A. (internship)
  • Johannes Osterhoff, M.A.
  • Dipl.-Inf. Zalan Kramer

Our group

Left to Right: Nadine Steinmetz, Johannes Osterhoff, Dr. Harald Sack, Jörg Waitelonis, Christian Hentschel, Bernhard Quehl

Publications

Scheduling Refresh Queries for Keeping Results from a SPARQL Endpoint Up-to-Date

Knuth, Magnus; Hartig, Olaf; Sack, Harald in Proc. of the 15th International Conference on Ontologies, DataBases, and Applications of Semantics (ODBASE 2016) 2016 .

Many datasets change over time. As a consequence, long-running applications that cache and repeatedly use query results obtained from a SPARQL endpoint may resubmit the queries regularly to ensure up-to-dateness of the results. While this approach may be feasible if the number of such regular refresh queries is manageable, with an increasing number of applications adopting this approach, the SPARQL endpoint may become overloaded with such refresh queries. A more scalable approach would be to use a middle-ware component at which the applications register their queries and get notified with updated query results once the results have changed. Then, this middle-ware can schedule the repeated execution of the refresh queries without overloading the endpoint. In this paper, we study the problem of scheduling refresh queries for a large number of registered queries by assuming an overload-avoiding upper bound on the length of a regular time slot available for testing refresh queries. We investigate a variety of scheduling strategies and compare them experimentally in terms of time slots needed before they recognize changes and number of changes that they miss.
2016Knuth-ODBASE.pdf
Weitere Informationen
Tags SPARQL Semantic_Web Web_3.0 its

Projects and Partners

 

  • AV-Portal Gottfried-Leibnitz-Universität Hannover, project with Technische Informationsbibliothek Hannover (TIB)
  • Semantic Media Explorer (SEMEX)
    The Semantic Media Explorer is a demonstrator that combines the latest media analysis processes to provides optimal access to video content.
  • MEDIAGLOBE Project
    The aim of MEDIAGLOBE is to open and interlink heterogenouse and currently isolated information sources in media archives and broadcasting corporation. Project partners: DEFA-spektrum, Medienbildungsgesellschaft Babelsberg mbH, Blue Order GmbH
  • THESEUS/CONTENTUS Project
    The purpose of CONTENTUS is to develop basic technologies with which to access, archive and search for multi-media cultural assets and works of art.
  • YOVISTO
    Yovisto is a video search engine specialized in academic content. Yovisto's search index is based on the combination of automated content based video analysis with user generated collaborative annotation (collaborative tagging, discussions, and comments). In difference to traditional video search engines, Yovisto enables pinpoint access within video data by providing fine-granular, time-dependent metadata.
  • Semantic Games
    Games with a purpose that are dedicated to create and curate semantic content.

Current News

Prior Events and Activities

 

2011

2010

2009

Teaching

 

 

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2014 (SS)

2013/14 (WS)

2013 (SS)

  • Seminar (Master): Semantic Multimedia (Blog)
  • Seminar (Bachelor): Multimedia Analyse Technologien (Blog)
  • Schülerkolleg (für Schüler der 8. bis 10. Klasse): Internetsuche und Google PageRank - Wie wird was durch wen gefunden?

    • Woche 1 - 09.04.2013: Die Geschichte der Web-Suchmaschinen (pdf)
    • Woche 2 - 23.04.2013: Term- und Dokumentenranking (pdf)
    • Woche 3 - 07.05.2013: Google Page Rank (pdf)
    • Woche 4 - 21.05.2013: Personalisierung und Web Crawling (pdf)
    • Woche 5 - 04.06.2013: Semantische Suche

 

 

2012/13 (WS)

2012 (SS)

2011/12 (WS)

2011 (SS)

2010/11 (WS)

2010 (SS)

2009/10 (WS)

 

 

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Supervised Master Theses

  • Gerald Töpper: Erweiterung der DBpedia Ontologie und des Extraction Frameworks zur Sicherung der Datenqualität. (finished April 2012)
  • Peter Retzlaff: Visualisierung von Bag-of-Visual-Words-Vektoren für die Visual Concept Detection (finished March 2014)
  • Sebastian Stange: Evaluierung einer semantischen Videosuche und Ermittlung geeigneter Videoanalysetechniken (finished March 2014)
  • Michael Wolowyk: Semantic Recommender Systems (preliminary title) (in progress)

Open Master Theses

Please find a list of possible topics for Master Theses. Contact us, if you are interested in one of these topics or have own suggestions.

  • Video Analysis:

    • OCR Spellcorrection
    • Tag Relevance Estimation in Photo Communities
    • Learning Local Image Descriptors

  • Linked Data and Semantic Web:

    • Named Entity Evolution
    • Authority File Mapping
    • A Mereology for Media Fragments

 

 

 

Press

 

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