re3dragon – A Research Registry Resource API for Data Dragons

Florian Thiery
Allard W. Mees

The re3dragon (REsearch REsource REgistry for DataDragons) FLOSS tool envisages two aims: first, publication of an archaeology related open extendable LOD resource catalogue including authority-data, thesauri, gazetteers, (space-) time gazetteers as well as typologies and domain-specific resources. 2nd, re3dragon offers an API for requesting distributed LOD resources, returning resources in a standardised JSON format based on JSKOS. The re3dragon is coded in JAVA and Open Source published on GitHub


Cartographers in historical maps used the phrase “Hic sunt dracones” (historically translated as: here be dragons) to describe areas which were beyond the known world of the map creator. Today, the digital data universe is full of unknown data, which have to be made FAIR (Findable, Accessible, Interoperable and Reusable) to integrate them in archaeological research. The World Wide Web offers researchers the possibility to share research data and enables the community to participate in the scientific discourse in order to generate previously unknown knowledge. However, much of this data is neither directly comparable and alignable nor easily findable or accessible, thus resulting in so-called modern unknown Data Dragons (Thiery et al. 2019). These Data Dragons lack connections to other data sets, which leads to a lack of interoperability and, in some cases, unusability. To overcome these shortcomings, a set of techniques, standards and recommendations can be used: Semantic Web and Linked Open Data (LOD) (Berners-Lee 2006; Schmidt et al. 2022) and consequently Linked Open Usable Data 1 (LOUD). To tame and unveil the modern data dragons, the CAA Special Interest Group (SIG) on Semantics and LOUD in Archaeology (SIG-DataDragon 2 ) was established in 2020. Data dragons require a safe location, what we call Dragon Lair, where they can be clustered and made accessible. This data dragon LOD lair location and its machine-readable accessibility are combined in the re3dragon tool - the REsearch REsource REgistry for DataDragons. The FLOSS 3 re3dragon tool envisages two aims. First, publication of an open extendable archaeology related LOD resource catalogue (the Dragon Lair) including authority data (e.g. Integrated Authority File - GND), thesauri (e.g. Getty AAT, Heritage Data Vocabularies), controlled vocabularies, gazetteers (e.g. GeoNames, Pleiades), space-time gazetteers (e.g. ChronOntology, PeriodO), as well as typologies and domain specific resources (e.g. Roman Open Data, Nomisma, Linked Open Samian Ware). 2nd, offering an API for requesting distributed LOD resources (so-called Dragon Items) providing resources in a standardised JSON format based on the JavaScript Object Notation for Simple Knowledge Organization Systems: JSKOS (Voß et al. 2016; Voß 2021). The tool is currently being implemented as part of the LEIZA digital research data infrastructure. It plays an essential role in the design of an overarching keyword registry (Meta-Index), which enables aggregating external distributed data resources in order to qualify internal data (e.g. the Meta-Index term Mainz may refer to Roman, mediaeval 4 or modern Mainz 5 , resulting in different aggregation references). This process to transform a vocabulary term into a label by linking it to reference thesauri concepts has been described in Piotrowski et al. (2014). This approach enforces interoperability and reusability, enabling mapping on external major union systems like Europeana. Moreover, these aspects play a pivotal role in the planned German National Research Data Infrastructure (NFDI) consortium NFDI4Objects 6 . Based on creating a JSKOS-enhancement (JSKOS+), re3dragon supports the furtherance of interdisciplinary major existing knowledge hubs such as the Basic Register of Thesauri, Ontologies & Classifications (BARTOC) 7 registry and the accompanying SKOS based mapping tool Cocoda 8 .


The re3dragon API is coded in JAVA using Maven and Apache Jena and is published Open Source on GitHub 9 (Thiery 2021). The re3dragon is based on the Labeling System approach (Piotrowski et al. 2014; Thiery and Engel 2016; Thiery and Mees 2023) and the re3cat API 10 .

The basis of re3dragon is an online catalogue of Linked Open Data resources (the Dragon Lair), which includes norm- and authority data resources (e.g. Getty AAT, Wikidata) as well as domain specific typologies and archaeological data (e.g. Terra Sigillata production centres, distribution sites, potters and ceramic typologies), stored as RDF in a RDF4J triplestore. Dragon Lairs are semantically modelled using the so called Linked Archaeological Data Ontology (LADO) which is based on the Research Software Engineering (RSE) Tools Ontology (Thiery 2019). Figure 1 demonstrates exemplary the Getty AAT Dragon Lair using the prefixes lado 11 and wd 12 :

The re3dragon offers three types of API services. 1st, a search API service for LOD resources with string and distance similarity; 2nd, an API resolving service for LOD resources related to specific URIs. 3rd, a catalogue API for Dragon Lairs. Service types 1 and 2 offer results according to the JSKOS+ format and HTML, and service type 3 provides an interoperable output integrable in research applications.

The JSKOS format defines a JavaScript Object Notation (JSON) structure to encode Knowledge Organisation Systems (KOS) (Voß 2021). JSKOS+ provides a standardised (Geo-)JSON(-LD) data model according to JSKOS which can be used in response to an API request. Figure 2 demonstrates the JSKOS+ JSON results for Getty AAT requests, showing the original JSKOS items in red and the added JSKOS+ items in blue.

The re3dragon applied in a research application

The re3dragon tool has been applied in the ARS3D project 13 (Thiery and Rokohl 2021; Thiery et al. 2023), in which it enriched data related to late Roman African Red Slip Ware (ARS). As an example, an ARS vessel is generically described as a “bowl” with decorative motives of “Hercules” and “Victoria” (O.39446 14 ), which can be annotated using Getty AAT, IconClass and Wikidata items. The potform can be described as a bowl using Getty AAT item 300203596 and Wikidata Item Q15398 15 , cf. Fig 3 . The two features can be described as follows: Hercules: IconClass item 94L 16 (cf. Fig 4 ) and Wikidata item Q240679 according to (Zu Löwenstein 2015) “B / FT III” (Q110892402), (Armstrong 1993) “8.109” (Q110892540), and (Atlante 1981) “135” (Q110892520); Victoria: IconClass item 96A5 (VICTORIA) and Wikidata item Q308902 according to (Zu Löwenstein 2015) “N / FT III (Victoria)” (Q110892417) and Armstrong (1993) “8.100” (Q110892537).


During its usage in archaeological data enrichment projects, the re3dragon tool can be easily and demand driven enhanced by adding more Dragon Lairs. The tool is already embedded in the ongoing development of the so-called Meta-Index of the Römisch-Germanisches Zentralmuseum Mainz (Thiery et al. 2018; Thiery and Mees 2021).

This procedure enables future enhancements of the JSKOS standard, e.g. semantic location descriptions, mapping properties as well as space and time typologies (Dimensionally Extended 9-Intersection Model, Allen’s Interval Algebra, etc.).


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