DE -Lite - a New Corpus of Easy G erman: Compilation, Exploration, Analysis (2024)

Abstract: In this paper, we report on a new corpus of simplified German. It is recently requested from public agencies in Germany to provide information in easy language on their outlets (e.g. websites) so as to facilitate participation in society for people with low-literacy levels related to learning difficulties or low language proficiency (e.g. L2 speakers). While various rule sets and guidelines for Easy German (a specific variant of simplified German) have emerged over time, it is unclear (a) to what extent authors and other content creators, including generative AI tools consistently apply them, and (b) how adequate texts in authentic Easy German really are for the intended audiences. As a first step in gaining insights into these issues and to further LT development for simplified German, we compiled DE-Lite, a corpus of easy-to-read texts including Easy German and comparable Standard German texts, by integrating existing collections and gathering new data from the web. We built n-gram models for an Easy German subcorpus of DE-Lite and comparable Standard German texts in order to identify typical features of Easy German. To this end, we use relative entropy (Kullback-Leibler Divergence), a standard technique for evaluating language models, which we apply here for corpus comparison. Our analysis reveals that some rules of Easy German are fairly dominant (e.g. punctuation) and that text genre has a strong effect on the distinctivity of the two language variants.

## introduction the un convention on the rights of persons with disabilities (un-crpd) 1 states that obstacles to accessibility to "information, communication and other services" should be eliminated by state parties for people with disabilities (article 9). against this background, many countries have pushed for 1 https://social.desa.un.org/issues/disability/ crpd/ legislation to reduce the language barrier for people with learning difficulties foot_0 as one of the core measures in creating equal opportunities. in germany, different forms of simplified german have emerged including variants of a regulated, "easy" german ('leichte sprache') that are intended to make written information accessible for low-literacy readers @xcite @xcite ; bundesministerium der justiz und für @xcite . according to a recent policy of the german ministry for work and social affairs foot_1 , it is now requested from public institutions to provide information in (regulated) easy german alongside standard german. while people with disabilities are the only group whose right to accessible written information is statutory, it is often claimed that non-disabled people such as learners of german or older people, or even all people (netzwerk leichte sprache, 2022), profit from easy german. while a long-awaited move in language policy, there are a number of open questions both for the theory and the practice of easy german. there are several agencies providing guidelines about how to write in easy german and while there is a fair level of convergence, there is also some conflicting advice. also, it is unclear whether specific features such as avoiding pronouns or using only simple, paratactic conjunctions (see section 2.1) are indeed beneficial for comprehension and if so, for which specific target groups. overall, there is fairly little empirically grounded research about the use of easy german in particular. this is the motivation of the project we report on in this paper. our focus is on the exploratory research question: what are the typical features of easy german in lived practice? this involves empirical studies of authentic productions in easy german and other variants of simplified german. for this purpose, we have compiled the de-lite corpus from preexisting resources of different variants of simplified german and standard german, and extended it with additional texts from the web. this paper documents decisions made in the corpus compilation process, including how to address the challenge of duplicate identification. in addition, we present an exploratory, n-gram-based study in which subcorpora of de-lite consisting of comparable texts in easy german and standard german are compared revealing main characteristics of easy german. we think that the corpus, its description, and the empirical study are of interest for the development of inclusive language technology, and that insights of the german corpus and its compilation can be transferred to other languages. our overarching theoretical approach is rooted in information theory @xcite , a mathematical theory of communication, according to which language users modulate the information content of their messages @xcite , adapting their linguistic encodings to properties of both the channel (e.g. noise) and the recipient (audience design) (see e.g. @xcite . the link to easy german is a natural one: rules and recommendations for easy german can be considered intentional measures to reduce the information content (surprisal) of linguistic expressions/units, such as words, sentences or stretches of text. surprisal being correlated with processing effort, modulation of information content is a measure to adapt to a supposedly lower channel capacity of the target group(s) of easy german. we thus hypothesise that the information content of linguistic units should be smaller in easy german compared to standard language, indicated e.g. by a preference for high-frequency words, lower lexical density, lower vocabulary variation and syntactic and cohesive explicitness. to identify the specific properties of easy german, we compare it with standard german, employing selected informationtheoretic measures, such as relative entropy, a measure widely used in nlp for evaluating language models. the paper is structured as follows. in related work (section 2), we sketch the history of easy german, followed by a brief state-of-the-art on corpus-based work on easy language. in section 3 we introduce the de-lite corpus containing texts in simplified variants of german by describing corpus design, the challenge of harmonising existing resources, and the mathematical basis of our language modeling. section 4 complements the corpus description by presenting an exploratory, comparative analysis of two de-lite subcorpora of easy german and standard german. we conclude with a summary and discussion (section 5). ## related work the next section outlines the development of easy german as a highly restricted variant of german. ## corpus in order to re-use previously collected data as well as annotations and alignments, we merged parts of different existing corpus resources containing texts in variants of simplified german: deplain (stodden et al., 2023), geasy (hansen-schirra et al., 2021), webcorpus @xcite and leiko @xcite . the corpus is still under construction and further existing easy german corpora will be included, such as apa-rst @xcite and the simple german corpus @xcite . to further expand the corpus, we also collected html text as well as pdfs from additional websites, our main sampling criterion being date of publication: in order to ensure comparability and avoid date of publication as con-founding variable, we excluded texts that had been published before 2017. this is motivated by the assumption that easy german has undergone substantial changes with regard to its linguistic characteristics. one trigger for this has been the publication of linguistically founded rules and recommendations for easy german texts by forschungsstelle leichte sprache hildesheim (research unit easy german hildesheim) @xcite . in addition, there have been research projects that improved the general understanding of what exactly is comprehensible for the target groups of easy german, such as leisa @xcite . the collected data comprises different file formats and requires different methods of preprocessing. as for pdfs, we used the python library pymupdf to extract text and conducted additional manual cleaning. for webscraping, we used the python requests library, and beautifulsoup in order to parse the downloaded html files. we used the tcf version @xcite of the webcorpus data @xcite containing primary text as well as annotations and metadata, which we also parsed with beautifulsoup. ## corpus comparison: easy vs. standard german for an explorative corpus study, we use de-lite v1 (see section 3.4). we investigate the corpus data with the help of n-gram based kld computations along two dimensions: language variant with the two categories easy and standard, and text genre with the categories news and non-news. to this end, we compare what specific types contribute significantly to the overall kld of the respective dimension category. figure 1 shows a visualisation of the distinctivity (size) and relative frequency (colour) of individual types. in order to illustrate typical uses and functions of the distinctive terms in the respective subcorpora, we additionally draw on concordances and example sentences. 8 in a first step, we compare the easy german subcorpus to the standard german subcorpus without drawing on any additional metadata (see section 4.1). on the one hand, our data reveal that in easy german, particular care is given to establishing coherence. on the other hand, we find characteristics that illustrate the ways morphological and syntactic simplicity is ensured in easy german. subsequently, we show that our approach can be used to detect text-genre specific features within easy and standard german by comparing easy german news to easy german non-news and standard news to standard german non-news (see section 4.2). our results show that the characteristics that distinguish news from non-news in easy german only partly overlap with those that distinguish news from non-news in standard german. ## summary and conclusions we presented a new corpus documenting the lived practice in simplified german writing. on this basis we built n-gram language models of the strongly regulated variant easy german and of standard german. we applied relative entropy to analyse the differences between the easy german and standard german models and between text genres within the respective variant. we extracted typical features of easy german on different linguistic levels and detected text genre differences within easy and standard german. by analysing distinctive types and additionally drawing on sample sentences and concordances, we showed that many of the typical features of easy german can be traced back to efforts of improving coherence, e.g. by explicitly connecting sentences of a text or explaining difficult words. some other features of easy german displayed by our models are a direct consequence of syntactic or morphological simplification. by including metadata into our analysis, we detected overrepresentations of words and phrases in texts by individual publishers that cannot be considered typical features of easy german. moreover, we showed that text genre variation is expressed differently in easy vs. standard german. many of these findings are not surprising keeping in mind the rules and recommendations for simplifying text in german. others, however, such as the distinctivity of potentially ambiguous pronouns in easy german, are related to simplifications of another aspect, showing that simplifying text with regard to one feature can make it more complex with regard to another. our approach can thus be used to uncover linguistic features of easy german that have been overlooked so far. in a next step, we will use our insights about typical linguistic features of easy german to design psycholinguistic studies evaluating the comprehensibility of specific linguistic characteristics for people with learning difficulties, one of the main user groups of easy german. in the future, we will also apply our approach to simplified variants other than easy german (e.g. plain german or german texts addressing children) and to further text genres (e.g. lexicons or administrative text). our findings can be used to classify simplified text found on the web or generated by ai but not carrying any specific label, or to fine-tune simplification algorithms.