This document specifies interoperability requirements for personal health decision support (PHDS) services between actors in the PHDS environment, which include PHDS services, data providers, and PHDS clients. It includes requirements for data exchange, validation, and error handling among participants to support accurate and timely decision-making. It also describes the privacy and security considerations for PHDS. However, the specifics of how PHDS services are developed or implemented are not covered.