The De Jonge Wiki is a digital, scientific research database on the building history of Arenberg Castle in Heverlee, Belgium. As a prototype it is intended to show how information on complex structures can be presented according to today’s state of the art. The aim is to work according to international quality standards as well as making the information easily accessible to users. For this purpose, both MediaWiki and Wikibase were used as software. In this way, a user interface was created that is visually and functionally reminiscent of Wikipedia and can therefore be intuitively understood by users without prior knowledge while the corresponding semantic data is stored in a database in the background.
Das De Jonge Wiki ist eine digitale, wissenschaftliche Forschungsdatenbank zur Baugeschichte des Kasteels van Arenberg in Heverlee in Belgien. Als Prototyp soll sie zeigen, wie Informationen über komplexe Strukturen gemäß dem aktuellen Stand der Technik präsentiert werden können. Das Ziel besteht darin, nach internationalen Qualitätsstandards zu arbeiten und gleichzeitig die Informationen für Benutzer*innen leicht zugänglich zu machen. Zu diesem Zweck wurden sowohl MediaWiki als auch Wikibase als Software verwendet. Auf diese Weise wurde ein Interface erstellt, das optisch und funktional an Wikipedia erinnert und damit von Nutzer*innen ohne Vorwissen intuitiv verstanden werden kann, während die dazugehörigen semantischen Daten in einer Datenbank im Hintergrund gespeichert werden.
De Jonge Wiki, a look far back into history can illustrate the mechanisms associated with data carriers. Around the middle of the 6th century BC Croesus, the King of Lydia, minted his heraldic animals on standardized gold and silver blanks (Figure 1). This procedure initiated the era of coins as a currency. However, Croesus had not only created a means of payment, but also a data carrier, which contained information on the wealth or the geographic range of influence of a certain regime.In order to classify the considerations underlying the
However, payment transactions are only one field in which currently the exchange of information runs almost only digitally. As comfortable as the new, electronic forms of communication are for humankind living today, it remains unclear how information of our era will be usable in the long term. To interpret the cuneiform on a clay tablet, the hieroglyphs on a stone stele or the ancient Hebrew on a scroll, one must only know the respective writing system to be able to read it. But when it comes to reading a digital document one must not only provide the electronic hardware but also the matching software to simply make a text visible at all.
The transmission of our current knowledge to future generations is thus inseparably linked with electronic technology – and thus with the risk of being lost. The development of digital media shows how real and inherent this danger is. Who can run a floppy disk or a VHS video cassette today? With every transfer of data to a new medium, parts of information get lost. Around 400 AD a similar media change seems to have been one of the causes of the so-called ›loss of books in late antiquity‹ when bound codices of parchment replaced scrolls of papyrus. Thereafter 1,400 years had to pass until modern libraries had again comparable stocks as they are recorded for ancient libraries.
In the case of digitally stored data, there is another threat of loss that results from the programs with which the data is stored. Specialized software can often only be used with fixed-term licenses. If users do not have the corresponding license (anymore), the data is unreadable to them. The same applies to the further development of software. Due to the progress and development of programs, it is possible that data records cannot be opened only a few years or updates after they have been saved. Datasets that are not worked with, maintained, used or changed, are in danger of becoming lifeless mummies in digital sarcophagi, of which it is uncertain whether they can ever be recovered again.
In this regard, the very technical progress and digital development to store data generates gigantic centrifugal forces and corrosive powers that threaten the continued existence and further usability of records. Since these relationships are inherent to the system, it is important to look for ways to prepare information in such a way so that it can react as flexibly to these developments as possible and remain accessible for as many users as possible.
MediaWiki and the potent extension Wikibase of the Wikimedia Foundation were chosen. This selection offers the advantage that the required functions are tested, stable, and established by the daily use of millions of users of the Wiki community.In awareness of these challenges, the De Jonge Wiki was created as a prototype to prepare data according to certain specifications. As medium of choice, a freely accessible online database with English as operating language was selected, to be easily accessible for interested users. As a software, the open source and cost free products
MediaWiki software has a routine update path with only a few disruptive changes. In addition, there are a number of ways to export to a wide variety of formats, which is beneficial to the integrity and extensive use of the data. Furthermore, there is the potential for communication and automated alignment with similarly designed databases. Another important aspect is that other organizations that are interested can adopt and adapt the data management structure used here for their own projects.
Since April 2021, the De Jonge Wiki has been developed as part of a cooperation of the EU-funded PALAMUSTO project (Grant Agreement ID: 861426) with the Institute of Computer Science, Teaching and Research Unit for Programming and Modeling Languages of the Ludwig-Maximilians University of Munich (LMU) and the Raymond Lemaire International Center for Conservation (RLICC) of KU Leuven with support from the Institute of Technology Recruitment (ITZ) of the Karlsruhe Institute of Technology (KIT) and is still progressing.
2.1 Building History of Arenberg Castle
Figure 3) was a fitting choice for a case study because it is both well studied and of a manageable scale. The first mention of a castle in Heverlee dates back to 1371, although a fortified building can be assumed to have existed for centuries before that. The donjon of which we know from pictorial representations seems to have been built in the first half of the 15th century under Raas van Graven or Antoine I de Croÿ. The decisive expansion into a representative hunting lodge happened under William de Croÿ, probably between 1505 and 1520, when the southern wing with the two corner towers and significant parts of the western wing were built. The most important pictorial and written sources for the early history of the castle were created under the reign of Charles III de Croÿ around 1600.Arenberg Castle in Heverlee (
Master in Conservation of Monuments and Sites program at KU Leuven have been studying the architectural history of the palace. In projects such as the ArchDoc program on documenting findings of building archaeology, over 20 experts and staff members have collected rich experience over the years, which has been documented in various forms, some only in analogue form, some already in digital form. Pooling this knowledge and making an overview of the collected information available online is the task that the De Jonge Wiki aims to serve. As one of the honorary professors, Krista De Jonge led the various research projects over the entire period mentioned. On the initiative of the researchers of the Wiki project, she therefore agreed to the usage of her name for the database.For more than 25 years, professors, lecturers, and students of architecture or the
2.2 MediaWiki and Wikibase
 In this project, a digital, semantic research database was created for the building history of Schloss Weikersheim in Baden-Württemberg, Germany. This database was set up as a WissKI database following the ontology of CIDOC CRM. The digital infrastructure for this project was provided under the direction of Piotr Kuroczyński and Peggy Große at the University of Mainz.The documentation of the architectural history of Arenberg Castle builds on the findings and insights made by Jan Lutteroth and Frieder Leipold under the direction of Stephan Hoppe within the interdisciplinary cooperation project Kulturliegenschaften 4.0.
Wikidata. However, such collections of data sheets that are linked together according to the principle of knowledge graphs are difficult to grasp for human users without prior knowledge and education. They contain the danger to appear like reference deserts without a human touch and can have a repulsive effect – especially for researchers from the humanities.While the Weikersheim database was thus created with a software that has been developed for academic research, the database on the building history of Arenberg Castle was created with Wiki software. By doing so, two basic requirements were to be fulfilled above all others. The first requirement was the modelling of the data according to international standards, so that the records are machine-interpretable. For this, the software Wikibase was used, which also forms the basis for the semantic database
Virtual Research Environment (VRE) for the exchange between the different researchers involved. First projects with students also showed that the infrastructure of the De Jonge Wiki is particularly well suited for Peer Assisted Learning (PAL) in academic education, where students support each other with their respective skills in mastering a task. Another advantage of using an established software ecosystem is the variety of additional tools and functionalities, for example the accessibility for users with disabilities and their tools such as screen readers.Because of this, the second main concern of the project was to strive for a user interface based on Wikipedia, so that users will be spared the anxiety threshold of the new and unknown. Instead they should be able to move in an environment where design and functions are known to them from their daily use of Wikipedia. To achieve this goal, it was obvious to use MediaWiki, the same software with which Wikipedia is operated. In addition, it also offers all opportunities for joint editing and documentation of editorial changes that are offered by Wikipedia as well. It can thus be used as a
Wikimedia Commons. In this media repository, free-to-use images, sound documents and videos as well as other media such as 3D objects can be published. In digital infrastructures, which are based on Wikibase or MediaWiki as software, these media can be integrated as preview images by simple linking, while hosting and all related activities are taken over and provided by Wikimedia Commons. This not only has the advantage that the hosting is outsourced, but also that the media in question can also be found in an environment used by a wider public.An additional benefit of using Wikimedia Foundation software is the possibility of linking to other platforms besides Wikidata and Wikipedia, such as
iframes were tested. Firstly, Sketchfab, which proved to be technically straightforward. However, being a software from a commercial provider, this solution does not align with the FAIR/O principles and can only be used as a temporary solution. Therefore, for future integrations of digital 3D models as iframes, the use of the Kompakkt platform is planned. Kompakkt is an extension of the e-learning software ILIAS developed by the Department of Digital Humanities at the Faculty of Arts and Humanities of the University of Cologne. Another option is Semantic Kompakkt, a technical advancement of Kompakkt developed within the NFDI4Culture initiative. It is a free, open-source toolchain for viewing and enriching data of 3D models, and similarly to the De Jonge Wiki it uses Wikibase for processing statistical data. However, experiments in collaboration with Lozana Rossenova from the Technische Informationsbibliothek (TIB) in Hanover showed that using this infrastructure would have only made sense if Semantic Kompakkt had been implemented in the logic of the Wikibase records from the beginning of the De Jonge Wiki project. Nonetheless, this option presents a promising possibility for future projects.Due to the limited options for displaying 3D objects on Wikimedia Commons, three additional methods for embedding 3D files via
2.3 Data Structure
Relational Database Management System (RDBMS), in which entities are assigned different properties, in the style of different columns in tables. On the other hand, there are graph databases in which information is stored as knowledge graphs, that means as different entities that can be linked to one another by properties. One possible concept for such graph databases are Labeled Property Graphs (LPG), which means that the connection between certain entities is expressed in main properties which are attached to a node and additional simple key–value pairs: »Lauren Bacall (date of birth: 16.09.1924; place of birth: The Bronx) was married to Humphrey Bogart«. In contrast, information in Resource Description Framework (RDF) graphs is expressed in so-called semantic triples consisting of Subject–Predicate–Object: »Lauren Bacall was married to Humphrey Bogart; Lauren Bacall was born on 16.09.1924; Lauren Bacall was born in the Bronx.« This means that all entities are interconnected by a particular property, thus forming a semantic triple. The Wikibase division of the De Jonge Wiki is such an RDF database.Basically, it can be said that there are several options when creating a scientific research database. On the one hand, there is the
Figure 4) like coordinates, as it were. In a way, this approach corresponds to the traditional room books used in older architectural research and can provide the information given there in a more flexible and digitally networked manner.The structure of a castle is particularly suitable for a clearly defined and structured database with a hierarchy or taxonomy. In this case, the entire complex of the castle with its topography and all associated architectural facilities is defined as the highest level. The initials AC for Arenberg Castle as part of their name mark all elements that are components of this complex. The main buildings of the castle are referred to by the initials MC for Main Castle. This Main Castle is in turn divided into the various wings and construction volumes, each defined by initials, such as for example EW for the East Wing. These wings again consist of different floors as well as facades and roofs, such as the first floor expressed as 1F. At the lowest level are the individual rooms designated by the currently used room numbers. The entire name of letter pairs thus refers to the position of the room in question (
For each such architectural unit an entry was created in the De Jonge Wiki both as a MediaWiki file and as a connected Wikibase file. In the MediaWiki entry, the information is published as text and images in the style of Wikipedia and – if possible – gives an overview of the findings to the respective building history. In the Wikibase entry, however, statistical information is stored in the form of RDF knowledge graphs.
These relationships are modelled according to a defining system, a so-called ontology, as for example CIDOC CRM (Comité International pour la Documentation Conceptual Reference Model). In a database, an ontology forms the intended frame of reference, which is then filled with the contents of the respective data records. The Wikibase datasheets of the De Jonge Wiki are based on the ontology on which also Wikidata is based. This decision was made, on the one hand, because this type of data modelling is applied by an influential and internationally accepted structure as Wikidata and, on the other hand, because this ontology is not a rigid and hierarchical taxonomy, such as CIDOC CRM, but flat and flexible and can be adapted to the requirements of the respective records. This makes it easily possible to integrate new insights and research approaches seamlessly into existing data.
Figure 5), namely:Due to the aim that users should be able to make data entries in the De Jonge Wiki with as short a training as possible, the structure was deliberately kept as simple as possible. There are only three page categories in the frontend (
- architectural structures (rooms, floors, facades, roofs, wings)
- scientific sources (articles, research reports, scans and photogrammetric images)
- historical sources (archival records, artefacts and historical photos)
As already discussed, the architectural structures represent the basic units. In their Wikibase data sheets, statistical information such as length, width, maximum height and area are given, but also to which next higher category the architectural structure belongs (Property:P34 ›part of‹). In addition, it is indicated through which other rooms the room in question can be entered in the current situation (Property:P16 ›Accessible from‹).
All of this information is indicated on the frontend using a template and can be seen as an info box at the top right there. To get to the frontend, you simply have to click on the link in the data sheet at the bottom right. Conversely, to get from the frontend to the corresponding data sheet, there is the ›De Jonge Wiki item‹ function in the left-hand column, which takes users to the Wikibase data sheet.
Other important information given in the data sheet are references to scientific and historical sources where information about the architectural structure in question can be found. The cells with these references are linked directly to the entries on the relevant articles in the info box. These links are generated automatically by entering the titles of the articles in the Wikibase data sheet. However, the article pages of this source material are only visible in the frontend to users who are logged in. The reason for this access restriction is the fact that content in this category is specially affected by copyright and data protection law. Some of the research projects listed here were part of student education and are treated as personal data.
Further information and previous research results can be discussed in the text sections in the pages on the historical sources. In the case of written archival material, the scan of a page and both the transcription and a translation proposal can be displayed next to one another in a list.
Figure 9). Historical sources and scientific sources can also be linked directly to one another when the historical one is one of the main subjects of the scientific one (Property:P28 ›Main subject‹). In this way, one obtains a clear listing of all investigations that have already been carried out on a specific part of the architecture.In the case of scientific sources, on the other hand, usually only editorial information such as authors, year and place of publication or number of pages is given (
Thus, the De Jonge Wiki tries to prepare diverse research data according to the FAIR/O principles: Findable, Accessible, Interoperable, and Reusable with the help of free Open license software. By adopting the digital infrastructure developed as a prototype, other scientific projects or cultural organizations can prepare their data effectively and valuable and make it publicly accessible in a user-friendly way.
2.4 Open Questions and Challenges
Fortunately, when the basic considerations were implemented in a functioning database, all of the intended aspects could be set up without major problems. When the data was entered by student research assistants, it was found that the structure can be understood intuitively after a short briefing. This made it possible that the student research assistants could follow the underlying logic intuitively and suggest and implement their own additions in order to optimize the database. In practice, however, there were also some challenges that could not be optimally met within a very limited time and budget framework.
›Query Service‹ are not yet available at the De Jonge Wiki. This would have offered a simple, user-friendly possibility to design queries in the SPARQL scripting language via the dataset in Wikibase, as well as the graphic representation of these search results. In addition, overview pages cannot simply be generated in this way, for example a list of all items that are identified as rooms (Property:P2 ›instance of‹; Item:Q257 ›Room‹). In order to still be able to have a classification, the articles in the frontend must be tagged and marked in accordance with the categories in Wikibase. This requires a double administration, which may eventually result in inconsistent information.Even at the beginning of the implementation, it became clear that the web space, which was kindly provided by KU Leuven, did not enable an easy way to use the Docker version of Wikibase. This is mainly due to the fact that the University is primarily interested in protecting its own research achievements from access by third parties. A classic virtual machine (VM) service operation as an execution environment for Docker or other container systems was classified as too vulnerable in regard to data security. Therefore some practical additional services such as the
The fact that Docker cannot be used also means that software updates have to be installed manually with more effort, which is why a certain amount of expert knowledge is required in dealing with MediaWiki software. However, administrators often have experience in using these solutions, especially at universities which provide wikis to support teaching, and should therefore be able to cope with this challenge. The De Jonge Wiki is in the process of moving to an environment in summer 2023 where Docker and SPARQL queries can be used and where the data will be backed up on a local server for improved security.
In addition, once created, data types of properties cannot be changed afterwards. Inventory numbers that are created as a numeric data type cannot be converted into a textual data field afterwards. Also the search function for both namespaces of the wiki has not yet been completely standardized and only works in a case-sensitive manner.
It should also be emphasized that the software of the Wikimedia Foundation is designed for Creative Commons-licensed content, that is for content that can, in principle, also be shared. Data to which this does not apply, for reasons of copyright or personal rights, can only be made accessible to a limited extent as an article in a private area. However, this is only a protection for article pages. With the sites of individual files such as the images uploaded in the wiki, this function does not exist.
With the De Jonge Wiki, for the first time a user-friendly frontend based on MediaWiki was linked with a semantic database based on Wikibase with the help of a simple template, as was previously only implemented for the exchange between Wikipedia and Wikidata. When working with students, it became clear that these structures could be understood quickly and that it was possible to deal with them independently after a short introduction phase. The infrastructure tested in this project therefore has the potential to be used by organizations such as museums as an up-to-date tool for inventorying and documenting measures following the FAIR/O principles.
 On the other hand, the data records created in Wikibase can be read automatically and integrated into other databases. In this context, it must be noted that the De Jonge Wiki will only be searchable together with other Wikibase databases in common SPARQL queries after the forthcoming move to a new hosting. However, this is due to the hosting in the digital infrastructure of KU Leuven and can easily be avoided in the case of any similar projects.Using MediaWiki and Wikibase as software results in two further advantages. On the one hand, it is popular, long-lasting software that can be used free of charge and does not require licensing. One has to be aware however that the term ›long-lived‹ is very relative in the world of modern data sciences, since this kind of wiki system itself has only been in existence for a little over 20 years.
 At the LMU in Munich, the De Jonge Wiki served as central example in the seminar ›Renaissance-Architektur digital. Aktuelle Forschungen und ihre Unterstützung durch semantische Datenbanken‹ (09523) during the winter semester 2021/2022 by Prof. Stephan Hoppe. There, students edited their own content in the database. With Frieder Leipold and Max Kristen as members, the De Jonge Wiki is meanwhile also represented at the international Wikibase Stakeholder Group.The De Jonge Wiki is already proving to be a welcome opportunity to convey content. In the academic year 2021/2022, the data was used by the RLICC at KU Leuven for the training of master’s students in the modules ›Analysis, Registration and Documentation Techniques: ArchDOC‹ (H00W6A), ›Building Archeology: Integrated Project Work‹ (H01X8A) and ›Integrated Project Work 3‹ (H00X2A). In addition, as part of the Master of Digital Humanities training at KU Leuven, a collaboration with Prof. Andrew Vande Moere from the research group ›Research[x]Design‹ (RxD) took place in the study year 2021/2022, which deals with digital designs to convey and develop the Arenberg Castle. Within this project, the master students used the De Jonge Wiki for their research.
With the De Jonge Wiki, a database was created that can be used intuitively to move freely in a virtual castle and get detailed information on the building history. Another requirement was the possibility to save data records in the background in a semantic database that meets current international standards. These tasks have been accomplished convincingly.
WikiApiary. More information on the structure and logic of modeling the data can be found on the De Jonge Wiki help page. Further collaborations will show whether the prototype tested here could be used for similar databases as their digital infrastructure.Organizations or projects that are interested in the De Jonge Wiki as a prototype for scientific databases can find detailed information on the extensions and skins used in the online reference list
In Belgium, cent amounts are rounded to 5-cent multiples in retail since December 2019, so that one- and two-cent pieces are virtually no longer in circulation.
In May 2023, archaeological excavations uncovered the remains of the fortifications around the donjon (cf. Smitz 2023).
Cf. Brìes 1991.
This initiative was financed by the Baden-Württemberg Ministry of Finance as part of the first digital agenda for Baden-Württemberg (digital@bw 2018/19) and is intended to develop innovative approaches to cultural heritage. The partner directly involved in this case was the administration of the State Palaces of Baden-Württemberg, which is also a cooperation partner within the PALAMUSTO project.
Cf. Baru 2021.
Cf. Carusi / Reimer 2010.
Cf. e. g. Bayerische Schlösserverwaltung (ed.) 2021.
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- Fig. 1: Stater of Croesus, around 550 BC (16 mm, 10.76 g), minted in Sardis. [Photograph: Classical Numismatic Group, Inc. http://www.cngcoins.com. CC BY-SA 3.0]
- Fig. 2: Rome and the ›dark centuries‹, the history of libraries in the period of 300 BC until 2000 AD. [Chart: Bibhistor, CC BY-SA 3.0]
- Fig. 3: South facade of Arenberg Castle, above [image: KU Leuven / Koufopoulos et al. 2021]; aerial view of the main building, left [image: KU Leuven / Koufopoulos et al. 2021]; floor plan of the ground floor with color labeling of different structural units, right. [Image: atlas plan, KU Leuven, Technical Services]
- Fig. 4: Structure of the room designations in the De Jonge Wiki. [Chart: Frieder Leipold 2021]
- Fig. 5: Structural logic of the page categories. [Chart: Frieder Leipold 2021]
- Fig. 6: Example of a data sheet in the Wikibase database. [Screenshot De Jonge Wiki]
- Fig. 7: Example of a front-end article for a room. [Screenshot De Jonge Wiki]
- Fig. 8: Example of a front-end article on a historical source. [Screenshot De Jonge Wiki]
- Fig. 9: Example of a front-end article on a scientific source. [Screenshot De Jonge Wiki]