Papers & articles.
Peer-reviewed work on knowledge graphs, the Semantic Web, and decentralized data sharing.
- 01
Pseudonymity for Personal Data Stores: Pseudonymous WebIDs and Decentralized Identifiers
Gertjan De Mulder, Ben De MeesterARES 2025 Workshops, Lecture Notes in Computer Science vol. 15997, pp. 111–129, Springer · 2025Personal data stores such as Solid make users data holders, but their standards rarely address pseudonyms, which protect privacy during sharing while letting the holder prove their true identity later. The paper presents, analyzes and evaluates pseudonymity methods within Solid on a job-application use case with three flows (pseudonym generation, diploma verification with data minimization via Verifiable Credentials, and Proof-of-Ownership identity binding), comparing a Solid-native solution in which an external party leases Web-resolvable pseudonyms against ephemeral did:key pseudonyms. Data-flow diagrams plus STRIDE and LINDDUN analyses favour static identifiers because they avoid external parties; requirement validation shows both solutions meet most needs, but the WebID solution remains observable and the did:key solution cannot delete or manage pseudonyms.
DOI - 02
Towards Queryable Verifiable Credentials
Gertjan De Mulder*, Ruben Dedecker*, Ben De Meester, Pieter ColpaertISWC 2025 Companion Volume (Posters & Demos), Nara, Japan · 2025Digital credentials in wallets can only be queried by JSON keys, which blocks internationalization and alternative semantics. The paper adds a SPARQL query to the OID4VP authorization flow, evaluated over the combined RDF representation of a wallet's credentials — stored as named graphs with blank-node graph names so claims and proof graphs stay uniquely tied to their credential — and returns Verifiable Presentations containing the selectively disclosed claims. Claim retrieval converts RDF predicates to JSONPath pointers, so only a subset of SPARQL is currently supported; future work covers complex claim requirements and metadata for requested claims.
Paper - 03
The Open Circularity Platform: a Decentralized Data Sharing Platform for Circular Value Networks
Gertjan De Mulder, Els de Vleeschauwer, Ben De Meester, Pieter Colpaert, Olaf HartigKG4S 2024 – 2nd International Workshop on Knowledge Graphs for Sustainability, co-located with ESWC 2024, Hersonissos, Greece · 2024Circular value networks need information to flow between actors across domains, systems and data models, but semantic and technical interoperability are lacking, and centralizing to fix the technical side costs actors control over (and trust in) their data. The paper presents a decentralized platform in which RML maps existing company data to RDF, Solid pods share it securely, Verifiable Credentials ensure authenticity and integrity, and a Web application queries and verifies data across pods. Viability is shown with an online demonstrator over construction, electronics and textile use cases.
Paper - 04
Implementation-independent Knowledge Graph Construction Workflows using FnO Composition
Gertjan De Mulder, Ben De MeesterKGCW 2022 – International Workshop on Knowledge Graph Construction, co-located with ESWC 2022, Crete, Greece · 2022Knowledge graph construction is usually one task inside a larger workflow whose abstract description is tightly coupled to its execution; mapping languages bring interoperability and reproducibility to the mapping step only. The paper describes data-flow workflows as compositions of abstract, implementation-independent function descriptions in the Function Ontology (FnO), aligned with P-PLAN and PROV-O for provenance, and shows that a Function Ontology Handler can execute such compositions automatically across technology stacks.
Paper - 05
PROV4ITDaTa: Transparent and direct transfer of personal data to personal stores
Gertjan De Mulder, Ben De Meester, Pieter Heyvaert, Ruben Taelman, Ruben Verborgh, Anastasia DimouCompanion Proceedings of The Web Conference 2021 (WWW '21 Companion), demo, Ljubljana, Slovenia, ACM · 2021Personal data is scattered across service providers in heterogeneous formats, so it cannot be ported and user control is inhibited. The demo presents a Web application that transfers personal data into a user's Solid pod as Linked Data by composing RML.io (declarative access and mapping to RDF), Comunica (querying and enrichment) and Solid pods (storage). Unlike hard-coded transfer solutions, every pipeline component is configurable and automatically generates detailed provenance, which makes the transfer transparent and interoperable.
DOI