This chapter describes a middle-out approach to eHealth interoperability, with strong oversight on public health and health research, enabled by a uniform and shared content model to which all health information exchange conforms. As described in New Zealand's Interoperability Reference Architecture, the content model borrows its top level organization from the Continuity of Care Record (CCR) standard and is underpinned by the openEHR formalism. This provides a canonical model for representing a variety of clinical information, and serves as reference when determining payload in health information exchange. The main premise of this approach is that since all exchanged data conforms to the same model, interoperability of clinical information can readily be achieved. Use of Archetypes ensures preservation of clinical context which is critical for secondary use. The content model is envisaged to grow incrementally by adding new or specialised archetypes as finer details are needed in real projects. The consistency and long term viability of this approach critically depends on effective governance which requires new models of collaboration, decision making and appropriate tooling to support the process.