Introduction: Healthcare information systems’ (HIS) lack of interoperability remains a challenge and a barrier for important health-related events detection. While relevant techniques are based on medical standards and technologies, these techniques do not follow a holistic approach. The creation of a set of tools that fulfils the needs of interoperability is needed. Aim: The aim of this paper is to present the terminology service envisioned while defining the initial design of the Interoperability solution proposed for the CrowdHEALTH project. Methods: In the CrowdHEALTH project, specific subcomponents responsible for providing the appropriate functionalities have been designed: The rule engine for the implementation of the business logic, the Structure Mapping Service which is responsible for creating and managing the knowledge related to the link that exists between information structures, or mappings between them and the Terminology Service for providing a set of operations on medical terminologies used for the coding of medical knowledge, which fill the information structures. Results: Therefore, it is possible to provide a series of functionalities about these information elements found within more complex structures expressed in a local code and translated into other standardized medical terminology. Towards this end, CrowdHEALTH presents the terminology service envisioned in the context of the initial design of the interoperability solution. Conclusion: CrowdHEALTH project provides an infrastructure to convert the clinical information into meaningful data so that healthcare systems communicate effectively. This initial proposal will be further extended and tested during the project life circle.