Metadata is essential for organizing, managing and searching for information resources and has been a keystone of resource description and discovery. This book is designed to provide information professionals, paraprofessionals and students with up-to-date, practical knowledge and complex skills centering on metadata application in digital repositories and libraries. It explores emerging user-generated metadata (i.e., social tagging) and introduces mechanisms dealing with the exploitation of social tagging to enhance information discovery and user services.