From Dataset to Knowledge Graph: The "Chronology of Events 1940-1944" at the Academy of Athens
Creators: name: Spiliotopoulou, Maria
name: Stamou, Giorgos
name: Chortaras, Alexandros
name: Tzedopoulos, Yorgos
Publisher: name: Zenodo
Year: 2023
Subjects: Knowledge graphs
Semantic queries
Archival series

description: From Dataset to Knowledge Graph: The “Chronology of Events 1940-1944” at the<br> Academy of Athens<br> The poster deals with the curation of a collection created by the Modern Greek History<br> Research Centre of the Academy of Athens in Greece. The collection is based on an archival<br> series of the British Foreign Office from the period between the outbreak of the Greek-Italian<br> War (October 1940) and the end of the Nazi occupation in Greece (October 1944). Based on<br> this material, a detailed chronology was compiled, recording specific events, but also<br> information exchange, proposals, plans and reports by Greeks, British, Allies and resistance<br> organizations. The Chronology was published in two volumes.1 The entries were also captured<br> in a database that allows multiple searches and extraction of data beyond the indexes contained<br> in the publication. Yet this digitized collection had remained a closed corpus of information,<br> without any interconnection with relevant collections of other institutions.<br> Three years ago, the Chronology was incorporated in the action “The 1940s in Greece” of the<br> project APOLLONIS, in the framework of which the partners of the project, based on the<br> metadata of various collections pertaining to that period, created common indexes and<br> knowledge bases to increase the collections’ accessibility and interoperability, and to familiarize<br> researchers with the possibilities of datasets curation.<br> Οne of the outcomes of this action was a linked data-based knowledge graph representation of<br> the collections to support expressive semantic queries. The first step for the construction of the<br> knowledge graph was the production of linked data representations of the collections using a<br> mapping tool.2 The mappings used both standard and custom vocabularies to cover collectionspecific<br> modeling needs. The second step was the automatic enrichment of the items in the<br> knowledge graph with annotations, which were produced for three semantic dimensions (place,<br> time, person/organization) by applying NERD tools on the relevant fields. For the Academy of<br> Athens Chronology, these tools produced Geonames, TimeLine3 and Wikidata annotations. The<br> resulting knowledge graph was further extended with relevant vocabularies (eg. DBPedia,<br> Greek Historical Periods4) by including cross vocabulary equivalence alignments for identical<br> terms and containment alignments for temporal terms.<br> Through these annotations, the knowledge graph allowed unified multi-vocabulary searches<br> over all collections, expressed in any of the supported vocabularies. To exploit the knowledge<br> graph, a search application was built that supported combined cross collection queries over the<br> three dimensions. Through limited reasoning support, the application was able to also answer<br> semantic queries by exploiting the vocabulary hierarchies and other term categorizations.<br> 1 M. Spiliotopoulou &amp; P. Papastratis (eds), Chronology of Events 1940-1944. From the Documents of the<br> British Foreign Office, two vols, Athens 2002 and 2004 (in Greek).<br> 2 A. Chortaras, G. Stamou, D2RML: Integrating Heterogeneous Data and Web Services into Custom RDF<br> Graphs, LDOW@WWW 2018<br> 3 TimeLine vocabulary, http://sw.islab.ntua.gr/timeline/<br> 4 Greek Historical Periods vocabulary, Greek National Documentation Center,<br> https://www.semantics.gr/authorities/vocabularies/historical-periods/vocabulary-entries<br> Practical evaluation showed that, although the quality of the results depended on the quality of<br> the automatically produced annotations, and the complexity of the queries affected<br> performance, knowledge graph technologies can enable researchers to locate relevant material<br> through expressive queries exploiting the levels of abstraction provided by the underlying<br> knowledge. For the Academy of Athens, the outcome was particularly fruitful: firstly, its<br> collection participated in a rich knowledge graph that facilitated research on the specific period;<br> secondly, interconnectivity highlighted documentation inconsistencies that have to be adjusted<br> to improve the quality of semantic queries.