## 2 Related Work
### Data Sovereignty and Trust  
Data sovereignty, for a long time a somewhat fuzzy and mainly political term, has grown to have a more precise technical meaning: to remain in control of one's personal data. In the context of data exchanges in a digital service economy, this principle has become central to many dataspace concepts, with decentralized federation of participants with full control over their data up to the point of the actual exchange. Many requirements and challenges have been identified, among them the interoperability within the dataspaces, but also the trust among the participants [1; 2; 3; 4; 5], and even relating to data security after the exchange [6]. These challenges are also pertinent to our work. However, a critical aspect we must address--unlike previous efforts--is managing user _consent_, ensuring that individuals have explicitly agreed to allow their data to be used by third parties, such as for research purposes. The long-standing effort to realize such dataspaces culminated in the International Data Spaces (IDS) initiative ([[https://internationaldataspaces.org/](https://internationaldataspaces.org/)]([https://internationaldataspaces.org/](https://internationaldataspaces.org/)) (accessed on 5 December 2024)), whose concepts and implementations [7; 8] provided the basis for the Gaia-X specification documents. Aligned with the principles of GAIA-X, our work builds upon these efforts. However, GAIA-X provides considerable flexibility in how these principles are implemented. In Section 4, we will detail our specific implementation and the extensions we have developed for the medical domain. Gaia-X-based approaches have been demonstrated to be successful in some application domains, especially mobility [9] ([https://gaia-x4 ki.eu/en](https://gaia-x4 ki.eu/en) (accessed on 5 December 2024)), with promising approaches in others such as smart cities [10] and agriculture [11]. Many of these approaches not only exemplify implementations of GAIA-X concepts but also share a common technical foundation in the form of frameworks. However, the health domain requires specialized extensions, particularly for managing consent--an area addressed through the enhancements proposed in this paper. A detailed discussion of existing work and our contributions is provided in Section 2.2. Due to both conceptual shortcomings and the lack of extensions mentioned above, the same kind of successful general application of Gaia-X approaches has so far not be seen within the health domain, although it has been attempted, e.g., by [12]. Our paper introduces new conceptual and technical solutions, along with valuable lessons learned, to support the broader application of GAIA-X concepts in the health domain. Health is also a strong focus of the German Gaia-X-Hub, an official Gaia-X institution, since it was conceived with the majority of use cases situated in health [13], including two of its lighthouse projects, Health-X [14] and Team-X [15]. Through extensive scientific collaboration with these two projects, we identified similar challenges in applying GAIA-X to the healthcare domain. However, GAIA-X-Med, Team-X, and Health-X have each adopted slightly different conceptual approaches and technical implementations. Our solution is detailed in Section 4.3, but a comprehensive comparison with the approaches developed by the other two projects remains for future work, as those initiatives are still ongoing. Despite the many health-related efforts and the focus of the Gaia-X-Hub, successful Gaia-X-based approaches have not been demonstrated to the same degree as in other domains, and standardized, interoperable implementations have not appeared or been as widely used. Therefore, in this paper, we will show a different approach, to also provide Gaia-X services to the health domain, keeping in mind the important requirements identified in the earlier works reported on above. In addition to Gaia-X, thereave been other initiatives for providing trusted secure data infrastructures for the health domain.