Ontology-based information extraction is considered as an effective method to improve the performance of information extraction (IE) systems. For research and disbursal of customized healthcare services, a major challenge is to efficiently retrieve and analyze the individual patient data from a large volume of heterogeneous data over a long span of time. This requires effective ontology-based information retrieval approaches for clinical information systems. This book is an attempt to highlight the key advances in ontology-based information retrieval techniques especially in the healthcare...