Johannes Schäfer


2024

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Hierarchical Adversarial Correction to Mitigate Identity Term Bias in Toxicity Detection
Johannes Schäfer | Ulrich Heid | Roman Klinger
Proceedings of the 14th Workshop on Computational Approaches to Subjectivity, Sentiment, & Social Media Analysis

Corpora that are the fundament for toxicity detection contain such expressions typically directed against a target individual or group, e.g., people of a specific gender or ethnicity. Prior work has shown that the target identity mention can constitute a confounding variable. As an example, a model might learn that Christians are always mentioned in the context of hate speech. This misguided focus can lead to a limited generalization to newly emerging targets that are not found in the training data. In this paper, we hypothesize and subsequently show that this issue can be mitigated by considering targets on different levels of specificity. We distinguish levels of (1) the existence of a target, (2) a class (e.g., that the target is a religious group), or (3) a specific target group (e.g., Christians or Muslims). We define a target label hierarchy based on these three levels and then exploit this hierarchy in an adversarial correction for the lowest level (i.e. (3)) while maintaining some basic target features. This approach does not lower the toxicity detection performance but increases the generalization to targets not being available at training time.

2023

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HS-EMO: Analyzing Emotions in Hate Speech
Johannes Schäfer | Elina Kistner
Proceedings of the 19th Conference on Natural Language Processing (KONVENS 2023)

2021

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Polarity in Translation: Differences between Novice and Experts across Registers
Ekaterina Lapshinova-Koltunski | Fritz Kliche | Anna Moskvina | Johannes Schäfer
Proceedings for the First Workshop on Modelling Translation: Translatology in the Digital Age

2020

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Computational Aspects of Frame-based Meaning Representation in Terminology
Laura Giacomini | Johannes Schäfer
Proceedings of the 6th International Workshop on Computational Terminology

Our contribution is part of a wider research project on term variation in German and concentrates on the computational aspects of a frame-based model for term meaning representation in the technical field. We focus on the role of frames (in the sense of Frame-Based Terminology) as the semantic interface between concepts covered by a domain ontology and domain-specific terminology. In particular, we describe methods for performing frame-based corpus annotation and frame-based term extraction. The aim of the contribution is to discuss the capacity of the model to automatically acquire semantic knowledge suitable for terminographic information tools such as specialised dictionaries, and its applicability to further specialised languages.

2019

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Offence in Dialogues: A Corpus-Based Study
Johannes Schäfer | Ben Burtenshaw
Proceedings of the International Conference on Recent Advances in Natural Language Processing (RANLP 2019)

In recent years an increasing number of analyses of offensive language has been published, however, dealing mainly with the automatic detection and classification of isolated instances. In this paper we aim to understand the impact of offensive messages in online conversations diachronically, and in particular the change in offensiveness of dialogue turns. In turn, we aim to measure the progression of offence level as well as its direction - For example, whether a conversation is escalating or declining in offence. We present our method of extracting linear dialogues from tree-structured conversations in social media data and make our code publicly available. Furthermore, we discuss methods to analyse this dataset through changes in discourse offensiveness. Our paper includes two main contributions; first, using a neural network to measure the level of offensiveness in conversations; and second, the analysis of conversations around offensive comments using decoupling functions.

2016

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Acquisition of semantic relations between terms: how far can we get with standard NLP tools?
Ina Roesiger | Julia Bettinger | Johannes Schäfer | Michael Dorna | Ulrich Heid
Proceedings of the 5th International Workshop on Computational Terminology (Computerm2016)

The extraction of data exemplifying relations between terms can make use, at least to a large extent, of techniques that are similar to those used in standard hybrid term candidate extraction, namely basic corpus analysis tools (e.g. tagging, lemmatization, parsing), as well as morphological analysis of complex words (compounds and derived items). In this article, we discuss the use of such techniques for the extraction of raw material for a description of relations between terms, and we provide internal evaluation data for the devices developed. We claim that user-generated content is a rich source of term variation through paraphrasing and reformulation, and that these provide relational data at the same time as term variants. Germanic languages with their rich word formation morphology may be particularly good candidates for the approach advocated here.