8 Association of Research Libraries Research Library Issues 302 — 2021 However, there are other identifiers besides ORCID that can be used to identify researchers. ResearcherIDs and Scopus Author IDs are two examples unlike ORCID, they are used in commercial databases (Web of Science and Scopus, respectively) and are not openly available. In the case of institutional identifiers, Research Organization Registry (ROR) IDs are freely and publicly available in the ROR registry, which provides an open data set and includes additional tools for working with institutional data, such as an open application-programming interface (API). Other identifiers for institutions also exist but they are not openly available, such as those in the Ringgold database and in Web of Science and Scopus. It is important to understand the differences between open and non- open PIDs because they speak to real risks and inconsistencies in our current landscape. Therefore, our focus is on those PIDs that have broad adoption globally and that allow use and reuse of the metadata they contain. The Importance of PIDs and Connected Metadata A PID itself should not be seen as the end goal. Instead, the power of PIDs is not so much what they identify as the connections they enable. These connections, and the insights they offer, can only be fully realized through open metadata and open infrastructure. As co-authors of a September 2020 report, Implementing Effective Data Practices: Stakeholder Recommendations for Collaborative Research Support,3 we presented a set of recommendations for implementing and advocating for PIDs in research infrastructure as a way to “unlock discovery.” A premise of the report is that PIDs are an essential element in building a more open research ecosystem. To fully realize this vision, systems and services that use or provide PIDs must follow open practices, particularly in terms of the open licensing of metadata: Organizations that sustain identifier registries are essential pieces of scholarly infrastructure, and beyond adoption and use of PIDs, these