<p>Vital sign assessment is a central step in clinical decision-making for monitoring and handling patient health status. However, the lack of interoperability among heterogeneous vital sign monitoring devices remains a major challenge in healthcare systems. To address this issue, this study recommends a Semantic Web of Things (SWoT)–based framework for vital sign interoperability, including the development of a semantic model that defines relevant medical domain classes, relationships, and attributes, along with an implementation approach. A prototype application was developed using a mobile application as frontend and a web-based backend, and its applicability was validated in a real-world clinical setting. Following ethical approval from the Addis Ababa Health Office, the validation was conducted at Tirunesh Beijing Hospital, Addis Ababa, Ethiopia, with informed consent obtained from all participating patients. Real-time data were collected from outpatients for hypertension classification using two wearable devices (for body temperature and heart rate measurement) and one non-wearable device (for blood pressure measurement). Patients were classified into four categories: normal, elevated, stage I hypertension, and stage II hypertension. This study presents validation of a SWoT model using real-world hospital data for hypertension classification. The results demonstrate the practicality of the proposed framework and its ability to enable unified access to heterogeneous devices and data formats, highlighting the potential of SWoT to improve interoperability in healthcare applications.</p>