This book will provide readers with the essential information needed to understand knowledge representation with a focus on healthcare. The book will use health sector real world examples to delineate the principal issues and solutions for the field of data representation. The book will include a history of terminologies and in particular their use in healthcare. This book will cover the basis, authoring and use of reference terminologies including the formalisms needed to use them safely. The editor will exhaustively cover the field of concept-based indexing and will provide readers with an understanding of natural language processing and its application to health terminologies. The book will discuss terminology services and the architecture for terminological servers. This text will serve as the basis for a course or equally well as a reference text.