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Auflistung nach Autor:in "Hagen, Matthias"

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  • Zeitschriftenartikel
    Answering Comparative Questions with Arguments
    (Datenbank-Spektrum: Vol. 20, No. 2, 2020) Bondarenko, Alexander; Panchenko, Alexander; Beloucif, Meriem; Biemann, Chris; Hagen, Matthias
    Question answering platforms such as Yahoo! Answers or Quora always contained questions that ask other humans for help when comparing two or more options. Since nowadays more and more people also “talk” to their devices, such comparative questions are also part of the query stream that major search engines receive. Interestingly, major search engines answer some comparative questions pretty well while for others, they just show the “standard” ten blue links. But a good response to a comparative question might be very different from these ten blue links—for example, a direct answer could show an aggregation of the pros and cons of the different options. This observation motivated our DFG-funded project “ACQuA: Answering Comparative Questions with Arguments” for which we describe the achieved results so far, and ongoing activities like the first shared task on argument retrieval.
  • Zeitschriftenartikel
    Argumentation technology
    (it - Information Technology: Vol. 63, No. 1, 2021) Cimiano, Philipp; Hagen, Matthias; Stein, Benno
    Article Argumentation technology was published on February 1, 2021 in the journal it - Information Technology (volume 63, issue 1).
  • Zeitschriftenartikel
    Editorial
    (Datenbank-Spektrum: Vol. 16, No. 1, 2016) Hagen, Matthias; Stein, Benno; Härder, Theo
  • Zeitschriftenartikel
    On divergence-based author obfuscation: An attack on the state of the art in statistical authorship verification
    (it - Information Technology: Vol. 62, No. 2, 2020) Bevendorff, Janek; Wenzel, Tobias; Potthast, Martin; Hagen, Matthias; Stein, Benno
    Authorship verification is the task of determining whether two texts were written by the same author based on a writing style analysis. Author obfuscation is the adversarial task of preventing a successful verification by altering a text’s style so that it does not resemble that of its original author anymore. This paper introduces new algorithms for both tasks and reports on a comprehensive evaluation to ascertain the merits of the state of the art in authorship verification to withstand obfuscation. After introducing a new generalization of the well-known unmasking algorithm for short texts, thus completing our collection of state-of-the-art algorithms for verification, we introduce an approach that (1) models writing style difference as the Jensen-Shannon distance between the character n-gram distributions of texts, and (2) manipulates an author’s writing style in a sophisticated manner using heuristic search. For obfuscation, we explore the huge space of textual variants in order to find a paraphrased version of the to-be-obfuscated text that has a sufficiently high Jensen-Shannon distance at minimal costs in terms of text quality loss. We analyze, quantify, and illustrate the rationale of this approach, define paraphrasing operators, derive text length-invariant thresholds for termination, and develop an effective obfuscation framework. Our authorship obfuscation approach defeats the presented state-of-the-art verification approaches, while keeping text changes at a minimum. As a final contribution, we discuss and experimentally evaluate a reverse obfuscation attack against our obfuscation approach as well as possible remedies.
  • Textdokument
    Web Archive Analytics
    (INFORMATIK 2020, 2021) Völske, Michael; Bevendorff, Janek; Kiesel, Johannes; Stein, Benno; Fröbe, Maik; Hagen, Matthias; Potthast, Martin
    Web archive analytics is the exploitation of publicly accessible web pages and their evolution for research purposes—to the extent organizationally possible for researchers. In order to better understand the complexity of this task, the first part of this paper puts the entirety of the world's captured, created, and replicated data (the “Global Datasphere”) in relation to other important data sets such as the public internet and its web pages, or what is preserved thereof by the Internet Archive. Recently, the Webis research group, a network of university chairs to which the authors belong, concluded an agreement with the Internet Archive to download a substantial part of its web archive for research purposes. The second part of the paper in hand describes our infrastructure for processing this data treasure: We will eventually host around 8 PB of web archive data from the Internet Archive and Common Crawl, with the goal of supplementing existing large scale web corpora and forming a non-biased subset of the 30 PB web archive at the Internet Archive.