A New Aligned Simple German Corpus

Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics Volume 1: Long Papers, pages 11393–11412 July 9-14, 2023 ©2023 Association for Computational Linguistics A New Aligned Simple German Corpus Vanessa Toborek1 Moritz Busch1 Malte Boßert1 Christian Bauckhage1,2 Pascal Welke1,3 1University of Bonn, 2Fraunhofer IAIS, 3TU Wien {toborek, welke}@cs.uni-bonn.de {busch, mbossert}@uni-bonn.de christian.bauckhage@iais.fraunhofer.de Abstract “Leichte Sprache”, the German counterpart to Simple English, is a regulated language aim- ing to facilitate complex written language that would otherwise stay inaccessible to different groups of people. We present a new sentence- aligned monolingual corpus for Simple Ger- man – German. It contains multiple document- aligned sources which we have aligned using automatic sentence-alignment methods. We evaluate our alignments based on a manually labelled subset of aligned documents. The qual- ity of our sentence alignments, as measured by the F1-score, surpasses previous work. We publish the dataset under CC BY-SA and the accompanying code under MIT license. 1 Introduction Text in simple language benefits language learners, people with learning difficulties, and children that tend to have a hard time understanding original and especially formal texts due to grammar and vocab- ulary. Text simplification describes the problem of generating a simplified version of a given text while conveying the same matter (Siddharthan, 2014). This involves the reduction of lexical and syntactic complexity by various operations like deletion, re- wording, insertion, and reordering (Saggion, 2017). Text simplification can further entail additional ex- planations for difficult concepts and a structured layout (Siddharthan, 2014). To make language more inclusive, guidelines for simple versions of languages exist. In English, most notably, Ogden (1932) introduced “Basic En- glish”. In German there are two prevalent kinds of simple language: “Einfache Sprache” (ES) and “Leichte Sprache” (LS), both roughly translating to easy language (Maaß, 2020). LS has strict rules, including the removal of subordinate clauses, the insertion of paragraphs after each sentence and the separation of compound nouns with hyphens. ES is less restrictive and does not have a specific set of rules; instead, translators can work more liberally. However, the goal of both approaches is to improve the language’s accessibility. There exists work on rule-based approaches for text simplification in German (Suter et al., 2016), but the problem of text simplification can also be defined as a monolingual translation task. Then, the availability of data becomes a prerequisite in or- der to apply statistical machine learning models to it. Especially sentence-aligned text constitutes the backbone of neural machine translation. To the best of our knowledge, only the work of Klaper et al. (2013) presents a parallel sentence-aligned corpus in German created from public web data. Our work addresses the lack of data for text simplification in German and thus creates an aligned corpus of easy language and corresponding German texts. As there is no German equivalent to the Simple English Wikipedia, which provides cross-lingual references between Simple English and English ar- ticles, we had to rely on multiple sources offering a small number of articles in German as well as …

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