Persistent Identifiers (PIDs): Are there still important PIDs missing? Investigation on agreements with publishers

Persistent identifiers (PIDs) like DOIs, ORCID, and ROR have improved linking between scholarly articles, authors, and institutions, enabling better interoperability. However, these PIDs alone do not fully ensure transparency in open access publishing. Many articles are published under transformative agreements, memberships, or sponsorships, but metadata about these agreements is often missing, making it hard to verify why a Version of Record is open access. To address this, a central, openly accessible registry of publisher agreements is proposed, including metadata on institutions, timelines, and agreement types. Embedding this registry in existing infrastructures like the Electronic Journal Library (EZB) would allow repositories and service providers to reuse data efficiently. The openCost project complements this by defining a metadata schema for cost data and agreements, ensuring machine-readable, open formats and compatibility with global standards like DataCite. Agreement PIDs, similar to DOIs or RORs, are essential for linking articles to agreements. Implementations in institutional repositories and services like OpenAPC demonstrate feasibility.