The first, most general query that was executed consisted of searching the web for a list of prime ministers of Belgium. This search consisted of two stages. In a first stage, we consulted official and trusted resources in order to establish a factual baseline for the information on prime ministers. As of the moment of writing (July 2020), the official Belgian Federal Public service (FPS) website of the Chancellery of the Prime Minister thus yielded a chronological overview of prime ministers, which proved to be incomplete as it was missing the biographical descriptions of most prime ministers before 1979, as well as that of Mark Eyskens, who was prime minister in 1981 (Chancellery, 2020). Using the search window on the official website of the Belgian Parliament did not yield any results. However, a Google search did reveal the presence of a PDF document with an overview of Belgian governments since the Second World War on the website of the Parliament (Parliament, 2020). This document cannot be accessed through the website and is not up to date, as, at the moment of writing, it stays an orphaned web document fixed in time (2018). Finally, an academically peer reviewed and updated list of prime ministers was found through the website of the Royal Historical Commission of Belgium, which was founded in 1834 and has as its mission to provide access to written sources and studies related to the history of Belgium. One of these sources is the ‘Belelite’ database project (henceforth: ‘RHC-Belelite’), which was started in 2017 under the supervision of KU Leuven Professor Emmanuel Gerard (Aspeslagh, Verleden, Matheve, Heyneman, & Gerard 2020). This authoritative academic list of prime ministers since the independence of Belgium is used as a basis for further comparisons. With our academic baseline thus established, we executed a Google search for the term ‘List of Belgian prime ministers’, which returned a Wikipedia page with such a list as one of the first results. As Wikipedia provides a link to all language versions of any page, the associated pages in English, Dutch, French and German are easily accessible. Appendix Tables 1a, b offer a comprehensive comparison between the RHC-Belelite data and these Wikipedia lists of prime ministers.

In a second step, data including the edit histories were sourced from the English, Dutch, French and German language versions of the biographical pages of three selected prime ministers, with the aim of scrutinising problematic representations and examining the differences between and within the versions of these biographies. This changelog was accessed through the ‘View history’ tab in the top-right corner of each Wikipedia page. We limit our scope to three biographies out of approximately 70 possible historical holders of the office of prime minister, in order to leverage a more meticulous comparative analysis. The political figures under discussion here are Achille Van Acker, a socialist prime minister of multiple governments between 12 February 1945 and 3 August 1946, Leo Tindemans, a Christian-democrat leading multiple governments between 25 April 1974 and 20 October 1978, and Sophie Wilmès, the incumbent prime minister of Belgium who replaced Charles Michel on 27 October 2019 when he was elected president of the European council and who was the leader of a minority government between 17 March 2020 and 1 October 2020.

In our comparative investigation of these Wikipedia entries, we take into consideration any edits to the biographical text or the infobox (a boxed summary on the right-hand side of the Wikipedia page) that are documented in the page’s changelog. This notably includes changes in the text strings and hyperlinks referring to the office of Prime minister of Belgium. The detailed outcomes of this query are documented in Appendix Tables 2–4a–d.

A third and final step of data collection consisted of the creation of a list of Belgian prime ministers from Wikidata, with the objective of establishing a comparison between these Wikidata entries and the lists sourced from Wikipedia. A list of Belgian prime ministers with a record for each prime minister with start and end dates of their continuous mandates as PM was obtained by entering the relevant SPARQL queries into the Wikidata Query Service. A first query yielded a list of 72 entries (https://w.wiki/ZX4). As this list excluded the incumbent prime minister Wilmès, a second query was created to obtain the missing entry (https://w.wiki/ZXH). Appendix Tables 5a–d contrast the outcomes of these queries with the corresponding Wikipedia lists of prime ministers.

A general observation that can be made with regards to retrieving lists of Belgian governments and their prime ministers, is that for knowledge-seekers it is non-trivial to find an authoritative version of such a list. This can be explained by the lack of an official list of Belgian prime ministers, as well as some shortcomings in the available literature and resources, such as a lack of broad historical coverage, a lack of digital resources, and occasional errors (Aspeslagh et al., 2020). When we compare the different-language Wikipedia listings of Belgian governments and their prime ministers with the authoritative RHC-Belelite list (see Appendix Tables 1a, b), a further four types of problems can be discerned.

Firstly, the data reflect different interpretations as to who actually held the office of Prime Minister at different points in time. This is particularly the case for the listings of the first Belgian governments. According to RHC-Belelite for instance, the first Belgian government leader was Goblet (28 February 1831–23 March 1831). Yet according to all of the Wikipedia listings, Belgium’s first prime minister was De Gerlache. It should also be noted that there are inconsistencies in how the latter’s time in office is represented differently on the Dutch and French Wikipedias on the one hand, and the English and German ones on the other. Belgium’s second prime minister according to RHC-Belelite is De Sauvage, whereas the Wikipedia lists put forward Lebau as prime minister, again with diverging term dates between them. Similar problems can be observed in the descriptions of the governments under De Meûlenaere and Goblet d’Alviella.

Secondly, the data display a lack of consensus about what constitutes a successor of a new government under the same prime minister. RHC-Belelite for instance lists three governments with Jaspar as Prime Minister, whereas the Dutch, French and English Wikipedia lists discern only two, and the German Wikipedia list mentions only one. A knowledge-seeker is confronted with a similar disagreement among sources in the case of the governments of Pierlot, some of which worked from exile in London during the Second World War. While sources agree on the start date of the first Pierlot government and the end date of the last Pierlot government, RHC-Belelite lists seven governments within this timeframe, and the Wikipedia lists only attest to six governments. These differences stem from an apparent lack of a common definition of what constitutes a successor government versus a continuation of the same government with some of its ministers changed.

Thirdly, we can observe some discrepancies between the authoritative RHC-Belelite list and the Wikipedia entries stemming from what are most likely typographical errors. It appears, for instance, that days and months are switched around in the dates that mark the end of Tindemans I and the start of Tindemans II in the English Wikipedia list. According to RHC-Belelite, Tindemans II ends on 6 March 1977 (06-03-1977 in Day-Month-Year notation). The English Wikipedia, in contrast, puts forward 3 June 1977 (03-06-1977 in Day-Month-Year notation) as the end of Tindemans I and the beginning of Tindemans II.

Fourthly, differences can be observed in the represented start and end dates of governments. In this regard, a striking example that reflects the possible extent of discrepancies between Wikipedia-representations and authoritative sources, is that of the recent governments of Michel and Wilmès. After Charles Michel, the then prime minister of the government Michel II, was elected president of the European council and he was replaced as PM by Sophie Wilmès on 27 October 2019. Wilmès then led the government Michel II until she eventually became the prime minister of a new minority government on 17 March 2020. RHC-Belelite correctly lists three Belgian governments between 11 October 2014 and 31 July 2020: Michel I (11 October 2014–9 December 2018), Michel II/Wilmès (9 December 2018–17 March 2020), and Wilmès I (starting on 17 March 2020). The Dutch, French and English Wikipedia lists of Belgian prime ministers, by contrast, each demarcate two Michel governments and two Wilmès governments. This example demonstrates that the different sources hold contrasting interpretations of how successive governments can and should be represented: RHC-Belelite has adjusted its naming convention for the idiosyncrasy of this change of prime ministers, while the Wikipedia lists rigorously follow the Belgian political mores of naming governments after their prime minister. Consequently, the latter leads to a contradiction when there is a de-facto new prime minister, but not a new government. Zooming in on the data, it can indeed be seen that all sources agree on 11 October 2014 as the start date of Michel I. However, while RHC-Belelite states that Michel I ends on 9 December 2018, the English Wikipedia list has Michel I ending on 21 December 2018. The successor government is named ‘Michel II/Wilmès’ by RCH-Belelite, with a start date of 9 December 2018. The English Wikipedia list puts this start date on 21 December 2018. This is consistent with the end date of Michel I in either list. RHC-Belelite has ‘Michel II/Wilmès’ ending on 17 March 2020. The English Wikipedia has the same end date for Wilmès I. Thus, according to RCH-Belelite, the incumbent government at the time of writing this article is Wilmès I, but according to the Wikipedia lists it is Wilmès II.

Further differences and inconsistencies are foregrounded when we compare the different language versions of the Wikipedia listings of governments among each other (see Appendix Table 1a, b). Firstly, the data show important differences in the spellings of first names, which are sometimes adapted to the main language of the article, but not consistently. ‘Frans Schollaert’ on the Dutch, English and German Wikipedias for instance equate to ‘François Schollaert’ on the French Wikipedia. ‘Henri Carton de Wiart’ in the French Wikipedia becomes ‘Henry Carton de Wiart’ in the English version. Another example of inconsistent naming is the concatenation of ‘Van de Vyvere’ to ‘Vande Vyvere’ in the German Wikipedia. Similarly, there is a lack of systematicity in the naming of governments, which sometimes consist of a single name and sometimes of two names. The convention of using double names of governments (e.g. De Mûelenaere-Nothomb or De Theux-Malou) are mostly the result of adding a precursor or successor to a government name, except for the case of Poullet-Vandervelde in the English Wikipedia, which apart from the name of Prime Minister Prosper Poullet also includes the name of the minister of foreign affairs Emile Vandervelde.

Secondly, the different language versions display a lack of agreement on the start dates and end dates of governments, in particular in the case of the first three governments. The first Belgian government led by de Gerlache took office on 26 February 1831 according to the Dutch and French Wikipedia, but the German and English Wikipedia posit 27 February 1831 as the start date. The difference is larger with regard to the end date of this government, as the Dutch and French Wikipedia indicate 23 March as end date, but German and English Wikipedia mention 10 March 1831, a difference of almost two weeks. The successor government of Lebeau took office on 23 March 1831 in Dutch and French Wikipedia, whereas the German Wikipedia gives 28 March 1831 as start date but all three do mark 21 July 1831 as end date. Finally, the English Wikipedia declares 10 March as the start date. The Lebeau government ended on 21 July 1831 in every language except for the English Wikipedia, where it is presented as ending on 24 July 1831. Furthermore, the third Belgian Government of de Mêulenaere took office on 24 July 1831 according to the German and English Wikipedia, but according to the Dutch and French Wikipedia this happened two days later (26 July 1831). The latter gives as end date 17 September 1832, but the German and French Wikipedia mark 20 October as the end date of that government.

Finally, we can observe that as a result of the inconsistent splits or concatenations of governments across the different languages, the total number of Belgian governments since 1831 is different for several of the studied Wikipedia pages. The Dutch Wikipedia page thus lists 99 Belgian governments, the French version 98 governments, and the English version 96 governments. The German version does not give a ranking number to Belgian governments, but does rank the Belgian governments in historical order (Appendix Table 1a, b).

A deeper analysis of the individual biographical Wikipedia pages (including a comprehensive look into their development over time) reveals the extent of content and information differences of a Wikipedia biography in different languages. The structure, contents and edit histories of these pages testify to variances in what is considered appropriate, worthwhile and correctly sourced information to be included in biographies, as well as to the differences in the pace with which this information is edited or corrected.

For one thing, these discrepancies manifest themselves on the pages’ structural level. While preformatted templates for writing articles and categorising information exist on Wikipedia, editors are not obliged to follow them. Consequently, different versions of the same topic item, such as a biography, can consist of different sections, which in themselves might contain very different types of information. This, e.g., becomes readily apparent when we compare the different language versions of the biographical page of Sophie Wilmès (see Appendix Figure 3a–b for full renderings of the pages), or the corresponding infoboxes (see Figure 1).

The edit histories of the different language versions of the pages reveal a further diversity and debate about which information to include or exclude. Until 19 April 2007, e.g., the first sentence of the Dutch version of Achiel Van Acker’s biography referred to him as a ‘freemason’ (AVA:NL 2020). This qualification was removed, with one commenter explaining that Van Acker might as well be called a ‘broom binder’ or ‘basket weaver’. This relatively swift change contrasts with a rather joking reference to Van Acker’s lack of mastery of Hebrew when meeting then-prime minister of Israel, which was only removed from the Dutch page on 21 June 2013, after figuring online for nine years. The French version of the page even features a similar joke since 5 November 2005, albeit in its ‘anecdote’ section (AVA:FR 2020). The editors’ criteria for relevance thus seem rather heterogeneous, and the speed at which corrections are made differs between language versions.

A closer look at the edit histories of the biographies of Leo Tindemans shows some remarkable changes in the number of governments in which he participated. Tindemans was prime minister from 25 April 1974 till 20 October 1978. All his Wikipedia biographies were first created in 2004. Until the end of 2006 the Dutch biography referred to six governments (LT:NL 28-03-2004 @ 19:06 till LT:NL 14-11-2006 @ 08:44), thereafter it referred to only two governments. Until 2011, the French biography stated that he was prime minister, without mentioning the number of governments over which he presided (LT:FR 17-09-2011 @ 12:17), after which date the infobox mentions four governments. The German Wikipedia biography only refers to the fact that he was prime minister without referencing his governments (LT:DE 2020). The English Wikipedia changes the number of governments he led from six to two in November 2007 (LT:EN 05-11-2007 @ 19:12, LT:EN 10-11-2007 @ 01:31). When inspecting the Wikipedia pages of each government in the different languages at the time of writing, the Dutch Wikipedia has separate pages for two Tindemans governments (Tindemans I, II), whereas the French and German Wikipedias each have four pages (Tindemans I, II, III, IV). The English Wikipedia does not offer specific pages for governments led by Tindemans. Arguably, the reasons for these differences are political-cultural, and depend on whether or not a transformation from a minority government to a majority government (or vice versa), notably through participation of regionalist political parties, is interpreted as constituting a new government. Starting out as a minority government, the first Tindemans I government was enlarged with a regional Walloon government (Tindemans II) which quit after three years, returning Tindemans to lead a minority government (Tindemans III). After elections a new Belgian majority government was formed (Tindemans IV). The French Wikipedia considers these as four separate governments, whereas the Dutch Wikipedia groups the first three together into one government.

Immediately after becoming the prime minister the edit histories for some of the biographical pages of Sophie Wilmès add information about her ancestry. Since 1 November 2019, the French version features the statement that ‘her mother is Jewish and lost multiple relatives in the Shoah’, with a reference to the newspaper the Times of Israel (SW:FR 01-11-2019 @ 05:31). This statement is debated in the discussion section, which raises concerns about the relevance and potential privacy issues concerning such information. Similar references to Wilmès’ ancestry are made on the German and English pages, which also cite Israeli newspapers as their sources (SW:DE 29-10-2019 @ 21:08, SW:EN 28-10-2019 @ 19:11). The Dutch page, by contrast, mentions the professional credentials of Wilmès’ mother, but does not refer to religion (SW:NL 2020). Thus, in this case, the texts and discussions reveal different ideological stances to the subject matter.

The problems of classification that present themselves in the body of the pages are further reflected in the historical changes made to the pages’ hyperlink texts and infoboxes (see Appendix Tables 2–4a–d for an in-depth evaluation). A detailed but crucial piece of information to consider here, are the strings that classify the political figures under discussion as ‘prime ministers’, and the destinations to which these classifiers might lead. These strings display a high degree of variation over time and between language versions. On the Dutch page of Achiel Van Acker for instance, the string ‘premier van België’ (‘Belgian Prime Minister’) refers to a Dutch page that explains the role of ‘Eerste minister’ by contrasting it with the regional Belgian functions of Flemish ‘minister-president’ and the term used for the leader of the Dutch government (also ‘minister-president’) (Appendix Table 2a). In this version, there is no link to the aforementioned Wikipedia list of Belgian prime ministers. The French and English Wikipedia biographies do however alternate between referring to a detailed page on the role of ‘prime minister’ and the contextualising overviews of lists of prime ministers (Appendix Table 2b and Table 2d). The German page does not contain any hyperlinks from the string ‘Premierminister’ (Appendix Table 2c). Furthermore, this page never featured a summary infobox.

In addition to similar types of problems, the biographical pages of Leo Tindemans present a mismatch between the non-hyperlinked number in the succession of Belgian prime ministers, and the actual, correct number. A string such as ‘58^ste Premier van België’ (Appendix Table 3a) is thus ‘hard-coded’ by the writer of the article, and in no way connected to the numberings in the Wikipedia listings of Prime Ministers discussed earlier.

Finally, a particularly striking classification choice concerns the fact that the English Wikipedia page for Sophie Wilmès includes the prime minister in the list of ‘Jewish Belgian politicians’ (a category which exists only in English, Hebrew and Urdu), as well as the list of ‘Jewish Prime Ministers’ (a category that exists only in English, Hebrew, Urdu, and Vietnamese). However, apart from mentioning her mother’s Jewish ancestry, none of the actual biographical texts discussed above claims that Wilmès herself is Jewish.

The third level of representation (which could be considered the ‘deepest’ level), comprises the Wikidata knowledge graph. While Wikidata is intended to become one of the main knowledge bases for artificial intelligence systems, a close comparison of the retrieved data with the authoritative RHC-Belelite information reveals similar inconsistencies as the Wikipedia data (see Appendix Table 5a). One such inconsistency is the end date of the government of De Trooz, which is marked as 9 January 1908 in RHC-Belelite, but as 31 December 1907 in all of Wikipedia, and Wikidata.

Of particular interest here, however, are a number of discrepancies between the Wikipedia lists of prime ministers, and the corresponding Wikidata items (Appendix Tables 5b–d). When we, e.g., inspect the succession of the governments of Paul Vanden Boeynants by the government of Gaston Eyskens, a logical contradiction presents itself, as Wikidata lists two different start dates for this government (17 June 1968 and 17 July 1968) (Appendix Table 5b). The former date is consistent with the RHC-Belelite list, the latter is consistent with Wikipedia’s listing. A similar situation presents itself in the case of the governments Vanden Boeynants-Martens (Appendix Table 5c). Here as well, Vanden Boeynants’ premiership is contradictorily presented as ending on two different dates (3 April 1979 in RHC-Belelite as well as the German and English Wikipedia listings of Belgian prime ministers and 3 March 1979 in the Dutch and French Wikipedia listings of Belgian prime ministers). Finally, when we zoom in on the governments of Mark Eyskens, who succeeded the fourth Martens government, the start of the premiership of Mark Eyskens is likewise marked by two different dates (6 April 1981 in RHC-Belelite and 31 March 1981 in all Wikipedia listings of Belgian prime ministers) (Appendix Table 5d).

These detailed observations profoundly problematise the relation between Wikipedia and Wikidata, as it is obvious that both platforms are not as closely connected as their names would suggest. While Wikidata formalises some of the ontological categories that are also present in the Wikipedia data and biographical pages discussed earlier (such as start and end dates of governments), we can nonetheless observe problems on the level of the actual information content, that is, of the facts that fill these ontological categories. Arguably, the observed differences between the Wikidata items and same-topic Wikipedia information can be attributed to the fact that these projects do not necessarily share user communities (also see Wikidata, 2020 for a discussion on the relation between both projects).

Our ‘nitpicking’ of the knowledge representations of Belgian governments and their prime ministers yields four main findings concerning the individual platforms under investigation, as well as the relationships between those platforms. For one thing, the examined data suggest a lack of agreement between authoritative academic sources on Belgian governments and their leadership, and the information that is presented in Wikipedia. Moreover, it has been shown that, unlike the Wikipedia information, authoritative sources are not easily retrieved by knowledge-seekers through a traditional Google search. Next, the examined data show that for basic factual information, there can be disparity between the different language Wikipedia articles on the same topic, be they lists of governments and their leaders, or biographical pages dedicated to individual prime ministers. Furthermore, it has been demonstrated that there are significant differences between the information presented in Wikipedia and that in Wikidata, suggesting a rather loose-knit relation between both platforms. Finally, the different types of errors that were discussed span different categories, including problems of naming, classification, and linking.