In this paper, we propose an Interoperability Framework (IF) for Persistent Identifiers (PI) systems that addresses functions, roles and responsibilities needed to make heterogeneous PI systems interoperable. The fundamental steps, which provided the main inputs for the design of the model have been: 1) a survey on the use of PI among different stakeholder communities and 2) the definition of interoperability use cases and requirements. The IF is presented as a solution addressing the PI interoperability issues, which have been identified in the survey and have been translated into concrete use cases to serve as requirements for designing the model. Conclusions and intended future work close the paper