This book provides an extensive survey of the R-tree evolution, studying the applicability of the structure and its variations to efficient query processing, accurate proposed cost models, and implementation issues like concurrency control and parallelism. Based on the observation that "space is everywhere," the authors anticipate that we are in the beginning of the era of the "ubiquitous R-tree" analogous to the way B-trees were considered 25 years ago. Written for database researchers, designers and programmers as well as graduate students, this comprehensive monograph will be a welcome addition to the field.