In this research the demands for models used for sharing and (re-)use of patient-centered information in a national IT-architecture are covered. This is done through an explorative case-study of a Danish national eHealth project: 'the vision of Shared Medication Record (SMR)'. The foci are on three stated objectives; interoperability of heterogeneous health data, transactional challenges, and interoperability assessment model. The dissertation uses demands for interoperability through a service-oriented architecture. Overall it is concluded that SOA-designed WS to ensure transversal interoperability for interdisciplinarity can be deployed in e-Health. The challenge of heterogeneity in health data can be minimized through applying SOA-designed WS.