LetterSampo – Historical Letters on the Semantic Web: A Framework and Its Application to Publishing and Using Epistolary Data

Epistolary data about historical letters are typically distributed in different archives depending on where the letters were sent to and received, and the data are represented using local heterogeneous data models and different natural languages. To study such letter data on a global level, the heterogeneous, distributed data in local siloes need to be aggregated and harmonized into larger services where local metadata can enrich each other to complement missing information. This article presents a new framework, LetterSampo, for representing, publishing, and using epistolary data as Linked Open Data (LOD) on the Web for Digital Humanities (DH) research. The framework is used for creating LOD services and for building individual LetterSampo portals on top of them. To test and demonstrate the framework, it has been applied to the epistolary CKCC dataset of ca. 20,000 letters of the Huygens Institute, the Netherlands, to the correspSearch dataset of ca. 151,000 letters aggregated by the Berlin-Brandenburg Academy of Sciences and Humanities, and to the Early Modern Letters Online (EMLO) data of ca. 170,000 letters published by the University of Oxford. The CKCC and correspSearch datasets were published as LOD services, SPARQL endpoints, and as data dumps at Zenodo.org for re-use, and a demonstrational portal LetterSampo: Historical Letters on the Semantic Web was created based on this data. A novelty of the LetterSampo portals is to use faceted semantic search for filtering data of interest in flexible ways from multiple perspectives on two conceptual levels, and then visualize and analyze the results and data by seamlessly integrated data analytic tools - programming skills are not needed for using the portal. In addition to using the tools of the portal, the SPARQL endpoints can be used with modest knowledge about programming for DH research.