This paper presents the implementation and evaluation of the Data Capsule framework, a novel approach for achieving personal data sovereignty. Our framework uses formal knowledge representation to understand both the context of personal data collection across heterogeneous systems and define comprehensive usage policies - from access control to monetisation opportunities. As organisations increasingly collect and process personal data, individuals continue to lack effective mechanisms to control how their information is processed and/or shared across heterogeneous systems. We tackle this problem with two key contributions: (1) an ontology-based federation system that allows for seamless federation of personal data across databases using schema.org as a semantic foundation, and (2) a semantically driven dynamic usage control mechanism that allows individuals to define and enforce granular access rules. Our implementation demonstrates that effective personal data sovereignty can be achieved and serves as a foundation for future systems contributing to the empowerment of individuals in the digital economy.