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Reviewer: Christian Mancas

Few books warrant celebration—this is one of them. Not only is it the first book on temporal databases, it is exceptional. It gathers outstanding contributions by more than 30 major researchers in this increasingly important new field, providing both comprehensive introductions and up-to-date results of their recent and current work. The contents have been carefully selected, reviewed, and structured by a distinguished editorial board. Part 1 presents extensions to the relational data model (RDM), beginning with the historical RDM of Clifford and Croker and its associated historical extension of the relational algebra. Gadia and Nair's temporal model and TempSQL come next. Lorentzos then presents his interval-extended RDM. Navathe and Ahmed describe their temporal RDM and temporal SQL. Sarda's proposed historical SQL and Snodgrass's TQuel are discussed next. Tansel describes his generalized relational framework for modeling temporal data, including the associated temporal relational calculus and algebra. Part 1 ends with Gadia's summary of Ben-Zvi's pioneering work in relational temporal databases. Part 2 covers nonrelational temporal data models. Elmasri et al. extend the enhanced entity-relationship model. Wuu and Dayal do the same for OODAPLEX, the object-oriented version of the well-known functional data model DAPLEX. Segev and Shoshani's semantic temporal data model, based on time sequence collections, and its relational representation are then discussed. Ginsburg offers an overview of object and spreadsheet history models. Finally, Baudinet et al. propose temporal extensions to deductive databases. Part 3 focuses on implementation issues of temporal databases. It covers query and join processing and their optimization; timestamping, concurrency control, recovery, and differential query processing in rollback transaction-time databases; and various temporal indexes, including time-split B-trees, SR-trees, mixed-media R-trees, lopsided B+ trees, time index, two-level combined attribute/time index, and the monotonic B+ tree. Part 4 contains general language issues and other issues in temporal databases. The completeness of query languages for historical data models is addressed first. An overview of temporal reasoning, including consistency checking for temporal constraints, follows. Time granularity in temporal relations is dealt with algebraically. A glimpse of Tuzhilin's SimTL, the rule-based simulation language based on temporal logic, which relates temporal databases to knowledge-based simulation, closes this part by opening a door to what will probably become the approach of choice for any knowledge base management system. The book concludes with an impressive bibliography and a useful concise glossary. It would be difficult and probably unfair to single out any contribution to this excellent, ground-breaking book. Every chapter is clearly written, well structured, and illustrated with good examples and figures. Some deal primarily with the history of this exciting area, whereas others focus on future work and open issues. Some lay formal foundations and rigorous proofs, some provide algorithms, and others appeal to human intuition. One must read all of them to get the whole picture. The editors and the publisher, who had the idea, the courage, the determination, and the know-how to do it so well, deserve special mention, however. This book will be a must for any database researcher, professor, or student, for many years to come.