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It is well known that temporal data management is a relevant requirement for a large number of applications. Temporal data management requires addressing several issues, some of which have not been widely investigated. Among those issues, a relevant one is represented by valid-time indeterminacy. Valid-time indeterminacy refers to the fact that events may be recorded in the database for which it is not known the exact occurrence times. Even though several research efforts have been reported dealing with the more general problem of databases with incomplete or fuzzy information, the specific problem of indeterminacy in temporal data had not been much investigated. This paper represents the first, comprehensive solution that I'm aware of, to such an issue. I like very much this paper because it is the result of very deep and extensive work. The paper not only proposes an approach to represent indeterminacy in temporal data; it also proposes a syntactic and semantic extension to!
SQL, to show how the approach can applied to a real query language. In the paper the authors also describe how the proposed concepts can be applied to TSQL2 - a temporal extension of SQL. Another relevant contribution of the paper concerns the implementation techniques for the temporal operators proposed in the paper and results from an experimental evaluation. Another notable contribution of this paper is in the section on related work where the authors extensively compare their work with all relevant related research efforts, such as null value handling, disjunctive databases, probabilistic databases, fuzzy databases. Definitely, the authors have done an excellent job in positioning their research in a wider context.
Copyright © 2000 by the author(s). Review published with permission.