This book covers the principles, techniques and standards for online GIS, including online spatial information and data warehousing. It examines the idea of metadata and outlines why it is important today, especially in the context of online information. It explains the underlying methodologies, including relevant standards, and the tools and skills needed to manage metadata. Finally the subject is placed in the context of global GIS: putting data online; creating metadata; creating virtual data warehouses; geographic agents and spatial data mining. It includes detailed descriptions adn demonstrations of crucial processes, such as implementing spatial queries and map-building online.