This leads to the assumption that the vocabulary used in articles, not only in printed but also in online media, is changing. To be precise, we assume a (temporary) frequency rise for specific word forms that are associated with the all-encompassing coronavirus pandemic. This does not exclusively mean that we can observe word forms that have never been observed in every-day press language. Although some terminological vocabulary (esp. from epidemiology and virology) might find its way into every-day press language, it is also very likely that concepts from every-day language which usually play a secondary role are suddenly much more important.
To investigate all these effects of the coronavirus pandemic on German press language, we created three inter-connected resources which we will introduce below: a corpus of RSS feeds, a dynamic HTML site which presents further analyses on vocabulary diversity throughout the coronavirus pandemic ("cOWIDplus Analysis") and an online viewer application that allows exploration of frequency profiles through time ("cOWIDplus Viewer").
The names of the two resources are derived from "OWIDplus" (www.owid.de/plus), which is an experimental platform for multilingual lexical-lexicographic data, for quantitative lexical analyses and for interactive lexical applications within the "Online-Wortschatz-Informationssystem Deutsch" provided by the Leibniz Institute for the German Language in Mannheim (OWID, www.owid.de).
Since the beginning of 2020, we have been collecting a corpus of RSS feeds for 13 sources in German language: Focus Online (https://www.focus.de/), Frankfurter Allgemeine Zeitung (https://www.faz.net/), Frankfurter Rundschau (https://www.fr.de/), Süddeutsche Zeitung (https://www.sueddeutsche.de/), Neue Zürcher Zeitung (https://www.nzz.ch/), Spiegel Online (https://www.spiegel.de/), Der Standard (https://www.derstandard.at), tageszeitung (https://taz.de/), Die Welt (https://www.welt.de/), Die Zeit (https://www.zeit.de/). In addition to these more "traditional" news outlets, we included three outlets from editorial offices that have no counterpart in printed form with the same name: web.de, t-online.de, and heise.de. The sources were selected for popularity, variety in German-speaking countries (one source each from Austria and Switzerland), and political orientation (for example, the Frankfurter Allgemeine Zeitung is described as a conservative newspaper whereas the tageszeitung is known to have a left-wing orientation. Also, heise.de, a source with a strong focus on information technology, is included in the sample. We use a custom R (R Core Team, 2020) script and the XML package (Temple Lang, 2020) to collect the raw feed data. The RSS feeds are extracted every three hours. This leads to duplicated items in the collected data because some items can and will still be in the RSS feed after three hours. We exclude these items by only considering unique entries in the data structure. Note that this procedure could still leave "duplicates" in our data because sometimes the editorial staff decide to make changes to already published content (e.g., a small change in the title of an article). Technically, however, these count as new items in the source's RSS feeds and are therefore treated as separate entries in our corpus.
All titles and descriptions (short pieces of text that introduce the articles) are extracted from the sources' RSS feeds along with the associated publication timestamp. Due to differing timestamp formats, we have to normalize the timestamps using the R package lubridate (Grolemund & Wickham, 2011) . We discard the exact timestamp and only keep the day of publication. We exclude all punctuation from the titles and description (henceforth "texts") except hyphens because we want to keep compounds. HTML markup (e.g. <strong> or </strong>) that could be used in RSS feeds is also excluded from the texts. All characters are converted to lower-case.
A few specific items are excluded from the texts, mainly because they are very specific to certain sources. The following list is the comprehensive set of word forms that are excluded following the above-mentioned procedure: t-onlinede-redakteurin, t-onlinede-redakteur (redakteur is German for "editor", redakteurin is the female form), sport-live-blog, t-onlinede, focus-online-redakteurin, focus-online-redakteur, focus-online-reporter, spiegel-titelstory, fazsprinter, heise, derstandardat, km/h . Also, all YouTube links and digit-only wordforms are excluded. After these pre-processing steps, unigram and bigram frequency lists are created for each day.
Given the continuous nature of corpus collection, we can only provide a snapshot of the current (sub)corpus sizes. The following figures reflect the state of the corpus up to May 21 st , 2020.
Currently, the RSS corpus contains 10,455,026 tokens which are distributed over 279,791 types.
The corpus sizes for each month are summarized in Table 1 . (2) When the pandemic and its consequences are under control, the situation will normalize and the vocabulary in online news outlets will diversify again in a continuous way. The variables used to quantify vocabulary diversity will return to the pre-pandemic level.
The quantitative measures we use to operationalize the narrowing of the vocabulary are information-theoretic redundancy (Shannon, 1948: 14) , mean segmental type-token ratio (MSTTR, Johnson, 1944 : 3) and the accumulated token frequency share of the 100 most frequent word forms per day. The central idea of cOWIDplus Analysis is to update the resource each week with the language data up to this day and continuously evaluate the hypotheses. To enable the scientific public to replicate the analyses and to investigate further research questions, the following data is available for download on the cOWIDplus Analysis website:
(1) Daily frequency lists (currently only of unigrams), (2) weekly frequency lists (of unigrams) and (3) the daily values for the central measures mentioned above (redundancy, MSTTR, and top 100 frequency share). This data is also updated weekly.
Since cOWIDplus Analysis is only available in German, we will not go into more detail regarding the methods and the current results. More information is available on the website.
Providing the daily frequency lists (see previous section) is a first step to enabling other researchers to use the RSS feed data. However, the amounts of knowledge and resources that are necessary to deal with the data could pose an obstacle for many people who might also be interested in the data. Inspired by the popular Google Books Ngram Viewer (Michel et al., 2011) we created the cOWIDplus Viewer (https://www.owid.de/plus/cowidplusviewer2020/) which enables users without any programming knowledge to search the RSS corpus for specific words forms, strings within word forms or bigrams.
The Viewer is a web application built using the Shiny framework (Chang et al., 2020) . Shiny is an R package that allows to build interactive web apps from R. It comes with pre-defined HTML widgets that can be used to build an interactive browser-based user interface. On the server side, user input is processed within R and the results are returned to the user's browser.
The interface of the cOWIDplus Viewer is divided into two pages accessible via tabs at just below the title: the main page and the bigram finder page. Figure 2 shows a screenshot of the current English version of the cOWIDplus Viewer's main page. In this case, we wanted to keep the entry threshold as low as possible and opted against regular expressions in the search field (which is, as a side note, also preferable due to security and, for some regular expressions, performance reasons).
In fact, all special characters used in regular expressions are deleted from the users' inputs and white space around entries is trimmed before further processing. Instead of full-blown regular expressions, we opted for a simple switch where users can choose the type of search for unigram searches (bigrams are always searched exactly as entered by the user). The two options are exact matching (the internal search algorithm uses the regular expression ^<pattern>$ for this) and matching within other word forms. Furthermore, the user can choose a specific date range which is propagated to the x-axis of the frequency graph on the right, the table of absolute frequencies on the bottom and the downloadable data file. The last parameter sets the window size of the rolling mean calculation which is realized by the "frollmean" function (with a centeraligned window) in the R package data.table (Dowle & Srinivason, 2019) and can be chosen between 1 (no smoothing) and 14 days. Due to the potentially lengthy calculations, we chose to use an action button ("Calculate") to trigger the calculation. Normally, Shiny applications are "reactive", i.e. start calculation whenever an input parameter is changed. Three download buttons give the user the opportunity to download the data which is currently displayed (a CSV file with daily absolute frequencies, relative frequencies and smoothed values), and two types of graphic formats of the plot (a 250-dpi PNG and a vectorized PDF). Each week, the underlying corpus is updated, so we have to make sure that the user is aware of the current date of the data.
On the right side of the main page, we show a graph of the relative frequencies in time which is smoothed if a window of greater than 1 day is selected for the rolling mean. If the user selects the search type "within-word-form", a table is displayed below the plot. This table shows all hits for all patterns, sorted by absolute frequencies within the selected date range. This table is quite important for this type of search because it might well be the case that the word forms that actually appear most often do not match the search patterns exactly. This is also the case in Figure 2 . The five most frequent word forms that are shown in the screenshot belong to the search pattern maske ("mask"). However, none of those hits is maske itself. There is maskenpflicht ("obligation to wear a mask"), masken (inflected form of maske), schutzmasken ("protective masks"), masked (part of the name of the TV show "The Masked Singer"), and atemschutzmasken ("respiratory masks"). The entry maske itself is ranked 7 th in terms of absolute frequencies with 510 hits. The table can be searched, sorted and the users can flip pages (not visible in Figure 2 ). Another example gives an impression of both a linguistically interesting case of naming conventions combined with a glimpse of political discussions. Figure 5 shows the developments in relative frequencies for the (partial) matches of ausgangssperre (curfew), kontaktverbot ("contact ban"), and lockerung ("relaxation"). The first mention of a potential curfew captured in the RSS corpus was on March 12 th . Afterwards, its frequency peaked on March 15 th .
However, a curfew was never implemented nation-wide in Germany. Instead, on March 22 nd , it was decided to implement a contact ban (which could be described as a much lighter version of a curfew). Although kontaktverbot never reached a peak as high as ausgangssperre, it was consistently more frequent than ausgangssperre for a prolonged time. Then, around mid-April, discussions about potential relaxations began which is reflected by a sharp increase of frequencies of lockerung. With certain relaxations becoming reality at the beginning of May, the frequencies increased even more. The last example shows how unigram and bigram searches can be mixed. In Figure 6 , relative frequencies for alltag ("every-day life") and neue normalität ("new normality") are shown.
Although alltag remains more frequent throughout the whole time period, the German-speaking online-press begins to include references to a certain neue normalität into their RSS feeds around the middle of April. It is quite reasonable to assume that it needed some time after the pandemic arrived in Germany that such a "new normality" is being established and written about.
The two examples in the previous section show that people with little or no knowledge about data manipulation and/or statistical programming are able to track some of the effects the coronavirus pandemic had and has on the vocabulary in the German-language online press. However, as time passes and the pandemic (hopefully) becomes less severe, its influence on press discourse is likely to diminish. Of course, this does not mean that the viewer will lose its relevance. On the contrary, a resource which can be used with little knowledge about programming and statistics to track the most recent changes in online press vocabulary with data that is updated on a weekly basis can be very useful even in "normal" times.
A related resource that was recently released is "The Coronavirus Corpus" that is part of the English-Corpora.org suite of corpora (https://www.english-corpora.org/corona/). This corpus consists of English articles harvested from the web that deal with the coronavirus. We are looking forward to interesting comparisons with our German-language resource. Note, however, that we did not make any restrictions on which items from the RSS newsfeeds are incorporated in our corpus. On a more general level, the NOW corpus (https://www.englishcorpora.org/now/) -of which the Coronavirus Corpus is a subset of -provides an excellent case in point for the assertion made above that resources that make it possible to track real time changes in a corpus, are of great value both in linguistics and in the digital humanities.
Another interesting corpus resource is currently being built at the Center for digital lexicography of the German Language (ZDL). The idea of the "coronakorpus" is to collect language data from relevant URLs from a range of publication sources in the German language (e.g., blogs, forums, tweets, and general information websites on the topic but also online newspaper articles). As for the "Coronavirus Corpus" mentioned above, the text has to deal with the coronavirus pandemic to be incorporated into the corpus.
We presented three inter-connected resources aiming to capture, analyze and explore recent German RSS news feed data since the beginning of 2020. The primary data source is the RSS corpus which is used both in cOWIDplus Analysis and the cOWIDplus Viewer. The former is a static HTML page that is updated on a weekly basis and seeks to analyze how the diversity of the vocabulary is developing in the light of the coronavirus crisis. The latter is an online application that enables both researchers and the broader public without data processing and analysis skills to explore the development of word forms through time.
As time passes and the impact of the coronavirus crisis on language presumably becomes much weaker than in March and April, we believe that the Viewer will still prove to be a valuable tool to explore a historical record of German press language during a global crisis.
Also, it enables the research community to compare the effects of such a (hopefully) singular event like this global pandemic to other events with large-scale implications (e.g., the US presidential elections later in 2020). In addition, we argued that the Viewer can also be used to analyze developments in vocabulary as close to real-time as possible. One obvious expansion of the scope would be to include more RSS sources in the corpus. This would expand the coverage of German language sources but would also allow the construction of corpora for other languages.