FAIR-Driven Retrospective Metadata Enrichment for KCDC Digital Resources

The KASCADE Cosmic-Ray Data Centre (KCDC) is an established open data archive in astroparticle physics with more than a decade of experience in long-term data preservation. It aims to apply modern technologies to maximise the accessibility, usability, and scientific value of research data for a broad audience, from professional researchers to students, citizen scientists, and science enthusiasts, while advancing the use of FAIR (Findable, Accessible, Interoperable, Reusable) practices. Operating within a data-intensive high-energy physics environment, we address community-wide challenges such as the large data volumes produced in astroparticle physics and the complexity of formats like ROOT and HDF5, which require domain-specific software and specialised approaches for machine-actionable metadata extraction. To support interdisciplinary discovery and integration into infrastructures such as PUNCH4NFDI, we extend established metadata with additional discovery-oriented elements and references, including domain knowledge historically dispersed in scientific publications. In this contribution, we present an enhanced metadata model for KCDC digital resources featuring expanded use of persistent identifiers and increased semantic connectivity. ... mehrWe also demonstrate how natural language processing and large language models support retrospective metadata enrichment for archival KASCADE datasets.