Purpose and properties of the JSKOS data format for knowledge graphs
Abstract
The JSKOS data format (JSON for Knowledge Organization Systems) was first created in 2014, mainly to encode SKOS and mappings between semantic artifacts in web applications. Since its initial draft it has been extended and implemented in applications such as Cocoda mapping tool, BARTOC terminology registry and DANTE terminology registry. The format has since been extened with features such as concept occurrences, annotations, and qualified statements, to become a knowledge graph data format in its own right, and it has become a core part of the infrastructure for controlled vocabularies at VZG. This presentation will outline the motivation behind JSKOS and illustrate its core capabilities and limitations. The role of JSKOS for authority files and data integration at VZG and NFDI will be shown and it will be compared with alternative knowledge graph formats such as RDF, RDF-star, property graphs, and the data model of Wikibase.
Full text
JSKOS Data Format at SWIB (2025-11-19) Purpose and properties of the JSKOS data format for knowledge graphs SWIB 2025 conference Jakob Voß 2025-11-19
JSKOS Data Format at SWIB (2025-11-19) Introduction
JSKOS Data Format at SWIB (2025-11-19) Terminology ▶Such as: classifications, thesauri, ontologies… ▶Known as: terminologies, knowledge organization systems, semantic artefacts, concept schemes, knowledge graphs… ▶Core idea: things, not strings ▶Done with: URIs, labels & links between
JSKOS Data Format at SWIB (2025-11-19) JSKOS In a nutshell ▶Encoding SKOS and related artefacts (concepts, mappings, concordances…) in JSON ▶Established infrastructure for controlled vocabularies at VZG ▶Mature specification at https://gbv.github.io/jskos/ JSKOS 0.7.0 just released yesterday
JSKOS Data Format at SWIB (2025-11-19) Background and motivation ▶Project coli-conc (2013-): infrastructure for (mappings between) knowledge organization systems ▶Cocoda web application combines terminologies, mappings, annotations via APIs in the client ⇒JSON ▶Integration of federated data ⇒RDF
JSKOS Data Format at SWIB (2025-11-19) Influences and references ▶SKOS for core classes and properties ▶JSON-LD and existing ontologies (DCAT, vCard, XKOS, SSSOM…) for URIs and mapping to RDF ▶Skosmos and other APIs ▶Wikibase Data Model ▶Standards:Web Annotation Data Model for annotations, GeoJSON for geospatial data, IIIF for media, RFC 6570 for URI Templates, XSD for Data Types…
JSKOS Data Format at SWIB (2025-11-19) JSKOS Features by examples
JSKOS Data Format at SWIB (2025-11-19) Concepts { "type":[ "http://www.w3.org/2004/02/skos/core#Concept" ], "notation":["641" ], "uri":"http://dewey.info/class/641/e23/", "prefLabel": { "en":"Food & drink", "de":"Essen und Trinken" } } Class 641 from Dewey Decimal Classification (DDC)
JSKOS Data Format at SWIB (2025-11-19) Mappings { "type":["http://www.w3.org/2004/02/skos/core#exactMatch" ], "from": { "memberSet":[{ "uri":"http://dewey.info/class/641/e22/", "prefLabel":{"en":"Food & drink" } }] }, "to": { "memberSet":[{ "uri":"http://www.wikidata.org/entity/Q118451828", "prefLabel":{"en":"food and beverage" } }] }, "justification": "https://w3id.org/semapv/vocab/ManualMappingCuration", "tool":[{"url":"https://coli-conc.gbv.de/cocoda/" }] }
JSKOS Data Format at SWIB (2025-11-19) Qualified statements {"prefLabel":{"en":"Göttingen" }, "qualifiedRelations": { "http://www.wikidata.org/entity/P17":[{ "resource": { "uri":"http://www.wikidata.org/entity/Q183", "prefLabel": { "en":"Germany" } }, "rank":"preferred", "startDate":"1990-10-03", "source":[{... }] },{ "resource": { "uri":"http://www.wikidata.org/entity/Q713750", "prefLabel": { "en":"West Germany" } }, "rank":"normal", "startDate":"1949-05-23","endDate":"1990-10-02" }]} }
JSKOS Data Format at SWIB (2025-11-19) Qualified statements ▶Inspired by Wikibase data model ▶Ranking (preferred/normal/deprecated) ▶References ▶Arbitrary fields, identified by URIs ⇒Full knowledge graph format ▶Flexibility & extensibility at cost of full interoperability
JSKOS Data Format at SWIB (2025-11-19) Closed world statements ▶missing field: unknown ▶[]: no value exists ▶[..., null]: more values exist
JSKOS Data Format at SWIB (2025-11-19) Applications of JSKOS
JSKOS Data Format at SWIB (2025-11-19) Use cases ▶Cocoda,BARTOC,DANTE… at VZG ▶NFDI4Objects & TS4NFDI ▶Slowly being adopted outside of VZG (2 or 3 implementations)
JSKOS Data Format at SWIB (2025-11-19) Applications & Libraries ▶jskos-server: DBMS to store JSKOS data ▶jskos-vue: widgets to nicely display JSKOS objects in browser (e.g. tree) ▶jskos-proxy: serve and browse JSKOS data (terminologies) as Linked Open Data ▶jskos-tools: helper functions for JSKOS data ▶jskos-cli: tools to validate and convert JSKOS data ▶subjects-api: query subject indexing of K10plus catalogue in JSKOS via JSKOS-API
JSKOS Data Format at SWIB (2025-11-19) JSKOS API Relevant, but not focus of this talk. ▶GET/POST/PUT/PATCH data in JSKOS format ▶Defined read & write endpoints for concepts, mappings, annotations… ▶Optional authentification included ▶Multiple implementations exist (servers and clients)!
JSKOS Data Format at SWIB (2025-11-19) Beyond JSKOS
JSKOS Data Format at SWIB (2025-11-19) Some limitations of JSKOS ▶Labels MUST have language tag (use und for undefined) ▶Notations don’t have data types ▶No support of SKOS Collections (yet?) ▶Fields about entities and metadata are mixed (e.g. startDate vs. created) ▶Wikibase data model only covered partially ▶No standards body behind the specification
JSKOS Data Format at SWIB (2025-11-19) Alternatives ▶Plain RDF or RDF* ▶JSON-LD ▶Property Graphs