The mission of HL7 Inc. is to provide standards for the exchange, management and integration of data that supports clinical patient care and the management, delivery and evaluation of healthcare services. The scope of this work includes the specifications of flexible, cost‐effective approaches, standards, guidelines, methodologies, and related services for interoperability between healthcare information systems. In the field of medical information technologies, HL7 provides the world's most advanced information standards.

Versions 1 and 2 of the HL7 standard have on the one hand solved many issues, but on the other demonstrated the size and complexity of the health information sharing problem. As the solution, a complete new methodology has been adopted, which is being encompassed in version 3 recommendations. This approach standardizes the Reference Information Model (RIM), which is the source of all domain models and message structures. Message design is now defined in detail, enabling interoperability between loosely‐coupled systems that are designed by different vendors and deployed in various environments.

At the start of the Primary Healthcare Information System project, we have decided to go directly to HL7v3. Implementing the HL7v3 standard in healthcare applications represents a challenging task. By using standardized refinement and localization methods we were able to define information models for Croatian primary healthcare domain. The scope of our work includes clinical, financial and administrative data management, where in some cases we were compelled to introduce new HL7v3‐compliant models. All of the HL7v3 transactions are digitally signed, using the W3C XML Digital Signature standard.